Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44.
The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and
very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose
of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF.
I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas.
For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m.
Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out.
I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks
Dave WB9YIG
Hello Dave,
you can do 2 things:
1. Add a highpass filter or bandpass filter in your receive path in order to suppress the 2m signal as good as possible. You can try first to insert the filter in front of your receiver (between the preamp and your receiver) and if that is not helping (enough) insert it in front of the preamplifier. Here is a link how to build such a filter: http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf
2. Add a lowpass filter to your 2m transmitter in order to reduce the harmonics emitted in the 70cm band as good as possible.
Kind regards
Matthias
www.dd1us.dehttp://www.dd1us.de
Von: Dave Julian via AMSAT-BB [email protected] Gesendet: Dienstag, 8. Februar 2022 17:41 An: [email protected] Betreff: [AMSAT-BB] IC-9700 and PS 70 not playing well together
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44. The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF. I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas. For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m. Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out. I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks Dave WB9YIG
Dave,
I use a comet duplexer CF-4160N to avoid desense issues. It acts as a bandpass filter with 60dB of rejection from your 2m TX. The dummy load is on there, because I read somewhere it acts better with one attached since it would expect to be connected to something vs open.
https://www.dxengineering.com/parts/cma-cf-4160n
[image: image.png]
73 -Ant NU1U
On Tue, Feb 8, 2022 at 11:41 AM Dave Julian via AMSAT-BB [email protected] wrote:
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44.
The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and
very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose
of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF.
I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas.
For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m.
Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out.
I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks
Dave WB9YIG
Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
Dave,
Try 2 without the picture. I guess first message was too large.
I use a comet duplexer CF-4160N to avoid desense issues. It acts as a bandpass filter with 60dB of rejection from your 2m TX. I use a dummy load load on there, because I read somewhere it acts better with one attached since it would expect to be connected to something vs open.
https://www.dxengineering.com/parts/cma-cf-4160n
73 -Ant NU1U
On Tue, Feb 8, 2022 at 11:41 AM Dave Julian via AMSAT-BB [email protected] wrote:
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44.
The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and
very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose
of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF.
I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas.
For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m.
Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out.
I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks
Dave WB9YIG
Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
Dave,
As Matthias suggested I highly recommend filters be added before the preamp, I mean between antenna and preamp..
I made many experiment with same. The reason is actually quite logical, your preamp will amplify both the wanted signal and also the 3rd harmonic from your Tx 2m transmission (which falls within the 70cm band) and possibly overload it) thus the wanted amplification at 70cm will be well below the noise created by your 3rd Tx harmonics (worse offender normally).
Just a suggestion and hope it work for your setup.
73
Jean Marc (3b8DU)
On Feb 8, 2022, at 9:06 PM, Matthias Bopp [email protected] wrote:
Hello Dave,
you can do 2 things:
Add a highpass filter or bandpass filter in your receive path in order to suppress the 2m signal as good as possible. You can try first to insert the filter in front of your receiver (between the preamp and your receiver) and if that is not helping (enough) insert it in front of the preamplifier. Here is a link how to build such a filter: http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf
Add a lowpass filter to your 2m transmitter in order to reduce the harmonics emitted in the 70cm band as good as possible.
Kind regards
Matthias
www.dd1us.de http://www.dd1us.de/
Von: Dave Julian via AMSAT-BB <[email protected] mailto:[email protected]> Gesendet: Dienstag, 8. Februar 2022 17:41 An: [email protected] mailto:[email protected] Betreff: [AMSAT-BB] IC-9700 and PS 70 not playing well together
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44. The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF. I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas. For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m. Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out. I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks Dave WB9YIG
Sent via AMSAT-BB(a)amsat.org http://amsat.org/. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/ https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org http://amsat.org/ Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org https://mailman.amsat.org/
Dave,
Forgot to say that bandpass filters at VHF and UHF normally have an insertion loss of a fraction of a dB (around <0.2 dB) thus the loss putting it in front of your preamp is negligible loss compared with the noise created by the 3rd harmonic of the 2m Tx.
Hope this also helps.
73
Jean Marc (3B8DU)
On Feb 8, 2022, at 9:31 PM, Jean Marc Momple [email protected] wrote:
Dave,
As Matthias suggested I highly recommend filters be added before the preamp, I mean between antenna and preamp..
I made many experiment with same. The reason is actually quite logical, your preamp will amplify both the wanted signal and also the 3rd harmonic from your Tx 2m transmission (which falls within the 70cm band) and possibly overload it) thus the wanted amplification at 70cm will be well below the noise created by your 3rd Tx harmonics (worse offender normally).
Just a suggestion and hope it work for your setup.
73
Jean Marc (3b8DU)
On Feb 8, 2022, at 9:06 PM, Matthias Bopp <[email protected] mailto:[email protected]> wrote:
Hello Dave,
you can do 2 things:
Add a highpass filter or bandpass filter in your receive path in order to suppress the 2m signal as good as possible. You can try first to insert the filter in front of your receiver (between the preamp and your receiver) and if that is not helping (enough) insert it in front of the preamplifier. Here is a link how to build such a filter: http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf
Add a lowpass filter to your 2m transmitter in order to reduce the harmonics emitted in the 70cm band as good as possible.
Kind regards
Matthias
www.dd1us.de http://www.dd1us.de/
Von: Dave Julian via AMSAT-BB <[email protected] mailto:[email protected]> Gesendet: Dienstag, 8. Februar 2022 17:41 An: [email protected] mailto:[email protected] Betreff: [AMSAT-BB] IC-9700 and PS 70 not playing well together
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44. The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF. I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas. For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m. Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out. I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks Dave WB9YIG
Sent via AMSAT-BB(a)amsat.org http://amsat.org/. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/ https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org http://amsat.org/ Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org https://mailman.amsat.org/
Dave,
Sorry for several mails, but what seems obvious to one is not necessarily well communicated as in this case (my fault).
Your filter and preamp should be as near as possible to the antenna, I put same at end of boom just behind the reflector element, the reason is simple which is to avoid the maximum of coax loss which seems to be a real issue in your case.
73
Jean Marc (3B8DU)
On Feb 8, 2022, at 9:41 PM, Jean Marc Momple [email protected] wrote:
Dave,
Forgot to say that bandpass filters at VHF and UHF normally have an insertion loss of a fraction of a dB (around <0.2 dB) thus the loss putting it in front of your preamp is negligible loss compared with the noise created by the 3rd harmonic of the 2m Tx.
Hope this also helps.
73
Jean Marc (3B8DU)
On Feb 8, 2022, at 9:31 PM, Jean Marc Momple <[email protected] mailto:[email protected]> wrote:
Dave,
As Matthias suggested I highly recommend filters be added before the preamp, I mean between antenna and preamp..
I made many experiment with same. The reason is actually quite logical, your preamp will amplify both the wanted signal and also the 3rd harmonic from your Tx 2m transmission (which falls within the 70cm band) and possibly overload it) thus the wanted amplification at 70cm will be well below the noise created by your 3rd Tx harmonics (worse offender normally).
Just a suggestion and hope it work for your setup.
73
Jean Marc (3b8DU)
On Feb 8, 2022, at 9:06 PM, Matthias Bopp <[email protected] mailto:[email protected]> wrote:
Hello Dave,
you can do 2 things:
Add a highpass filter or bandpass filter in your receive path in order to suppress the 2m signal as good as possible. You can try first to insert the filter in front of your receiver (between the preamp and your receiver) and if that is not helping (enough) insert it in front of the preamplifier. Here is a link how to build such a filter: http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf
Add a lowpass filter to your 2m transmitter in order to reduce the harmonics emitted in the 70cm band as good as possible.
Kind regards
Matthias
www.dd1us.de http://www.dd1us.de/
Von: Dave Julian via AMSAT-BB <[email protected] mailto:[email protected]> Gesendet: Dienstag, 8. Februar 2022 17:41 An: [email protected] mailto:[email protected] Betreff: [AMSAT-BB] IC-9700 and PS 70 not playing well together
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44. The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF. I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas. For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m. Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out. I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks Dave WB9YIG
Sent via AMSAT-BB(a)amsat.org http://amsat.org/. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/ https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org http://amsat.org/ Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org https://mailman.amsat.org/
Thanks for the input. I just happen to have one of the Comet filters so I will give it a whirl. I was suspecting the 3rd harmonic could be the issue. I plan on putting the pre-amp at the antenna as soon as mother nature gets rid of winter. Will let you folks know the outcome.
73//Dave WB9YIG
_____
From: Jean Marc Momple [mailto:[email protected]] Sent: Tuesday, February 08, 2022 12:01 PM To: Matthias Bopp Cc: Dave Julian; [email protected] Subject: [AMSAT-BB] Re: IC-9700 and PS 70 not playing well together - More from 3B8DU
Dave,
Sorry for several mails, but what seems obvious to one is not necessarily well communicated as in this case (my fault).
Your filter and preamp should be as near as possible to the antenna, I put same at end of boom just behind the reflector element, the reason is simple which is to avoid the maximum of coax loss which seems to be a real issue in your case.
73
Jean Marc (3B8DU)
On Feb 8, 2022, at 9:41 PM, Jean Marc Momple [email protected] wrote:
Dave,
Forgot to say that bandpass filters at VHF and UHF normally have an insertion loss of a fraction of a dB (around <0.2 dB) thus the loss putting it in front of your preamp is negligible loss compared with the noise created by the 3rd harmonic of the 2m Tx.
Hope this also helps.
73
Jean Marc (3B8DU)
On Feb 8, 2022, at 9:31 PM, Jean Marc Momple [email protected] wrote:
Dave,
As Matthias suggested I highly recommend filters be added before the preamp, I mean between antenna and preamp..
I made many experiment with same. The reason is actually quite logical, your preamp will amplify both the wanted signal and also the 3rd harmonic from your Tx 2m transmission (which falls within the 70cm band) and possibly overload it) thus the wanted amplification at 70cm will be well below the noise created by your 3rd Tx harmonics (worse offender normally).
Just a suggestion and hope it work for your setup.
73
Jean Marc (3b8DU)
On Feb 8, 2022, at 9:06 PM, Matthias Bopp [email protected] wrote:
Hello Dave,
you can do 2 things:
1. Add a highpass filter or bandpass filter in your receive path in order to suppress the 2m signal as good as possible. You can try first to insert the filter in front of your receiver (between the preamp and your receiver) and if that is not helping (enough) insert it in front of the preamplifier. Here is a link how to build such a filter: http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf
2. Add a lowpass filter to your 2m transmitter in order to reduce the harmonics emitted in the 70cm band as good as possible.
Kind regards
Matthias
www.dd1us.de http://www.dd1us.de/
Von: Dave Julian via AMSAT-BB [email protected] Gesendet: Dienstag, 8. Februar 2022 17:41 An: [email protected] Betreff: [AMSAT-BB] IC-9700 and PS 70 not playing well together
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44.
The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and
very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose
of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF.
I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas.
For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m.
Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out.
I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks
Dave WB9YIG
-----------------------------------------------------------
Sent via AMSAT-BB(a) http://amsat.org/ amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/ https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a) http://amsat.org/ amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org/ https://mailman.amsat.org
Here's a handy link. Don't think I saw it thus far in the thread...
https://www.amsat.org/a-simple-desense-filter-for-mode-j-satellites/
(second time Tony AA2TX (sk) enters our conversations today..)
Mark L. Hammond [N8MH] AMSAT Director and Command Station
On Tue, Feb 8, 2022 at 4:14 PM Dave Julian via AMSAT-BB [email protected] wrote:
Thanks for the input. I just happen to have one of the Comet filters so I will give it a whirl. I was suspecting the 3rd harmonic could be the issue. I plan on putting the pre-amp at the antenna as soon as mother nature gets rid of winter. Will let you folks know the outcome.
73//Dave WB9YIG
*From:* Jean Marc Momple [mailto:[email protected]] *Sent:* Tuesday, February 08, 2022 12:01 PM *To:* Matthias Bopp *Cc:* Dave Julian; [email protected] *Subject:* [AMSAT-BB] Re: IC-9700 and PS 70 not playing well together - More from 3B8DU
Dave,
Sorry for several mails, but what seems obvious to one is not necessarily well communicated as in this case (my fault).
Your filter and preamp should be as near as possible to the antenna, I put same at end of boom just behind the reflector element, the reason is simple which is to avoid the maximum of coax loss which seems to be a real issue in your case.
73
Jean Marc (3B8DU)
On Feb 8, 2022, at 9:41 PM, Jean Marc Momple [email protected] wrote:
Dave,
Forgot to say that bandpass filters at VHF and UHF normally have an insertion loss of a fraction of a dB (around <0.2 dB) thus the loss putting it in front of your preamp is negligible loss compared with the noise created by the 3rd harmonic of the 2m Tx.
Hope this also helps.
73
Jean Marc (3B8DU)
On Feb 8, 2022, at 9:31 PM, Jean Marc Momple [email protected] wrote:
Dave,
As Matthias suggested I highly recommend filters be added before the preamp, I mean between antenna and preamp..
I made many experiment with same. The reason is actually quite logical, your preamp will amplify both the wanted signal and also the 3rd harmonic from your Tx 2m transmission (which falls within the 70cm band) and possibly overload it) thus the wanted amplification at 70cm will be well below the noise created by your 3rd Tx harmonics (worse offender normally).
Just a suggestion and hope it work for your setup.
73
Jean Marc (3b8DU)
On Feb 8, 2022, at 9:06 PM, Matthias Bopp [email protected] wrote:
Hello Dave,
you can do 2 things:
- Add a highpass filter or bandpass filter in your receive path in
order to suppress the 2m signal as good as possible. You can try first to insert the filter in front of your receiver (between the preamp and your receiver) and if that is not helping (enough) insert it in front of the preamplifier. Here is a link how to build such a filter: http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf
- Add a lowpass filter to your 2m transmitter in order to reduce the
harmonics emitted in the 70cm band as good as possible.
Kind regards
Matthias
www.dd1us.de
*Von:* Dave Julian via AMSAT-BB [email protected] *Gesendet:* Dienstag, 8. Februar 2022 17:41 *An:* [email protected] *Betreff:* [AMSAT-BB] IC-9700 and PS 70 not playing well together
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44.
The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and
very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose
of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF.
I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas.
For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m.
Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out.
I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks
Dave WB9YIG
Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
Dave,
I also had bad interference to my IC-9700 while working sats & receiving on 435. I have SSB preamps installed at the antennas on both bands. My preamps power with separate injectors on the coax, not from the radio. The solution to the problem was to climb up on the roof and install the 2m/70cm diplexer on the input of my 70 cm preamp (as the AMSAT mode J tip page says). I also installed a second diplexer in the shack on the 2 meter side between the radio and DC injector to minimize the 3rd harmonic interference.
I still get some very minor interference when pointed specific directions (toward other antennas on my roof), but the problem is gone 95% of the time.
Ernie W8EH
On 2/8/2022 11:40 AM, Dave Julian via AMSAT-BB wrote:
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44.
The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and
very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose
of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF.
I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas.
For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m.
Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out.
I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks
Dave WB9YIG
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Thanks folks. Adding the Comet filter worked like a champ. The one I had uses UHF connectors and pigtails so with adapters it's a bit ugly but works. I'll get the N version to make it pretty before doing the final install on the tower.
73//Dave WB9YIG
_____
From: Mark L. Hammond [mailto:[email protected]] Sent: Tuesday, February 08, 2022 3:32 PM To: Dave Julian Cc: Amsat - BBs Subject: Re: [AMSAT-BB] Re: IC-9700 and PS 70 not playing well together - More from 3B8DU
Here's a handy link. Don't think I saw it thus far in the thread...
https://www.amsat.org/a-simple-desense-filter-for-mode-j-satellites/
(second time Tony AA2TX (sk) enters our conversations today..)
Mark L. Hammond [N8MH]
AMSAT Director and Command Station
On Tue, Feb 8, 2022 at 4:14 PM Dave Julian via AMSAT-BB [email protected] wrote:
Thanks for the input I just happen to have one of the Comet filters so I will give it a whirl. I was suspecting the 3rd harmonic could be the issue. I plan on putting the pre-amp at the antenna as soon as mother nature gets rid of winter. Will let you folks know the outcome.
73//Dave WB9YIG
_____
From: Jean Marc Momple [mailto:[email protected]] Sent: Tuesday, February 08, 2022 12:01 PM To: Matthias Bopp Cc: Dave Julian; [email protected] Subject: [AMSAT-BB] Re: IC-9700 and PS 70 not playing well together - More from 3B8DU
Dave,
Sorry for several mails, but what seems obvious to one is not necessarily well communicated as in this case (my fault).
Your filter and preamp should be as near as possible to the antenna, I put same at end of boom just behind the reflector element, the reason is simple which is to avoid the maximum of coax loss which seems to be a real issue in your case.
73
Jean Marc (3B8DU)
On Feb 8, 2022, at 9:41 PM, Jean Marc Momple [email protected] wrote:
Dave,
Forgot to say that bandpass filters at VHF and UHF normally have an insertion loss of a fraction of a dB (around <0.2 dB) thus the loss putting it in front of your preamp is negligible loss compared with the noise created by the 3rd harmonic of the 2m Tx.
Hope this also helps.
73
Jean Marc (3B8DU)
On Feb 8, 2022, at 9:31 PM, Jean Marc Momple [email protected] wrote:
Dave,
As Matthias suggested I highly recommend filters be added before the preamp, I mean between antenna and preamp..
I made many experiment with same. The reason is actually quite logical, your preamp will amplify both the wanted signal and also the 3rd harmonic from your Tx 2m transmission (which falls within the 70cm band) and possibly overload it) thus the wanted amplification at 70cm will be well below the noise created by your 3rd Tx harmonics (worse offender normally).
Just a suggestion and hope it work for your setup.
73
Jean Marc (3b8DU)
On Feb 8, 2022, at 9:06 PM, Matthias Bopp [email protected] wrote:
Hello Dave,
you can do 2 things:
1. Add a highpass filter or bandpass filter in your receive path in order to suppress the 2m signal as good as possible. You can try first to insert the filter in front of your receiver (between the preamp and your receiver) and if that is not helping (enough) insert it in front of the preamplifier. Here is a link how to build such a filter: http://www.dd1us.de/Downloads/Mode-J%20Filter%20rev1_1.pdf
2. Add a lowpass filter to your 2m transmitter in order to reduce the harmonics emitted in the 70cm band as good as possible.
Kind regards
Matthias
www.dd1us.de http://www.dd1us.de/
Von: Dave Julian via AMSAT-BB [email protected] Gesendet: Dienstag, 8. Februar 2022 17:41 An: [email protected] Betreff: [AMSAT-BB] IC-9700 and PS 70 not playing well together
Just got a new SSB SP 70 preamplifier for my IC-9700 and having an issue with working 435 RX satellites like RS-44.
The amplifier works fine but I am getting terrible overloaad from the 2M TX signal. It causes the OVF light to come on and
very distorted audio. I have lowered the RX gain and TX power on the IC-9700 but by that time it kind of defeats the purpose
of a preamplifier. My set-up is an M2 2MCP22 with fixed polarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF.
I have about a 200' run on LMR-400 to the base of the tower with lightning arrestors then about 40' of RG-213 to the antennas.
For testing I have the Sp 70 preamplifier temporarly installed at the base of the tower. No preamplifier for 2m.
Power to the preamplifier is over the coax from the IC-9700. I am looking any any suggestions on sorting this out.
I have removed the PS 70 at this point to avoid damage the radio or preamplifier.
Thanks
Dave WB9YIG
-----------------------------------------------------------
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Dave, not referring to your problem, do you notice a big difference when changing polarity? Wondered if it was worth the cost and effort to add polarity to my M2 antennas. Thanks for the info. Mike
-----Original Message----- From: Ant Lefebvre [email protected] To: Dave Julian [email protected] Cc: AMSAT BB [email protected] Sent: Tue, Feb 8, 2022 12:06 pm Subject: [AMSAT-BB] Re: IC-9700 and PS 70 not playing well together
Dave, I use a comet duplexer CF-4160N to avoid desense issues. It acts as a bandpass filter with 60dB of rejection from your 2m TX. The dummy load is on there, because I read somewhere it acts better with one attached since it would expect to be connected to something vs open. https://www.dxengineering.com/parts/cma-cf-4160n
73 -Ant NU1U
On Tue, Feb 8, 2022 at 11:41 AM Dave Julian via AMSAT-BB [email protected] wrote:
Just got a new SSB SP 70 preamplifier for my IC-9700 andhaving an issue with working 435 RX satellites like RS-44. The amplifier works fine but I am getting terrible overloaadfrom the 2M TX signal. It causes the OVF light to come on and very distorted audio. I have lowered the RX gain and TXpower on the IC-9700 but by that time it kind of defeats the purpose of a preamplifier. My set-up is an M2 2MCP22 with fixedpolarity on 2m and a 436CP30 with the PS-70Cm polarity switch for UHF. I have about a 200' run on LMR-400 to the base of the towerwith lightning arrestors then about 40' of RG-213 to the antennas. For testing I have the Sp 70 preamplifier temporarlyinstalled at the base of the tower. No preamplifier for 2m. Power to the preamplifier is over the coax from the IC-9700.I am looking any any suggestions on sorting this out. I have removed the PS 70 at this point to avoid damage theradio or preamplifier. ThanksDave WB9YIG -----------------------------------------------------------
Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
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Sent via AMSAT-BB(a)amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Acceptable Use and Privacy Policies available at https://www.amsat.org/about-amsat/
View archives of this mailing list at https://mailman.amsat.org/hyperkitty/list/[email protected] To unsubscribe send an email to amsat-bb-leave(a)amsat.org Manage all of your AMSAT-NA mailing list preferences at https://mailman.amsat.org
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