Good morning,
I was chatting with a friend about his experimentation with amateur satellites and have been pondering if his setup is "safe" for his radio. He is running an FT-847 through a duplexer (diplexer if you want to be pedantic) and into a dual-band vertical base antenna on his roof. Definitely not an ideal setup, but meant to be temporary until time and better weather allow. He has managed to make some FM contacts on AO-92 with it.
My concern is him using a duplexer in this manner while running full duplex. I suppose this is similar to what people must do if using an Elk antenna. I just worry about there being enough isolation between the ports and damaging his transceiver. Are there others using similar setups or is this something to avoid?
73, Alex VA3ASE
It’s not ideal, but there are plenty of worse things that one can do. Last time I tested some off the shelf diplexers on my former employer’s VNA, I found them to have 80-90db of isolation. That’s not bad.
On Tue, Feb 11, 2020 at 7:08 AM VA3ASE via AMSAT-BB [email protected] wrote:
Good morning,
I was chatting with a friend about his experimentation with amateur satellites and have been pondering if his setup is "safe" for his radio. He is running an FT-847 through a duplexer (diplexer if you want to be pedantic) and into a dual-band vertical base antenna on his roof. Definitely not an ideal setup, but meant to be temporary until time and better weather allow. He has managed to make some FM contacts on AO-92 with it.
My concern is him using a duplexer in this manner while running full duplex. I suppose this is similar to what people must do if using an Elk antenna. I just worry about there being enough isolation between the ports and damaging his transceiver. Are there others using similar setups or is this something to avoid?
73, Alex VA3ASE _______________________________________________ Sent via [email protected]. 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. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Even at 100 watts output and 60 dB of isolation (the rated isolation of off the shelf diplexers, though as you mention, they may be better), the maximum amount of transmit power that might possibly get back into the radio is -10 dBm or 100 uW (100 watts = 50 dBm - 60 dB of isolation = -10 dBm). That won't do any damage. Cheap off-the-shelf ATSC tuners are rated to handle something around -5 dBm for those living very close to extremely powerful television transmitters.
73,
Paul, N8HM
On Tue, Feb 11, 2020 at 10:13 AM Mike Thompson via AMSAT-BB < [email protected]> wrote:
It’s not ideal, but there are plenty of worse things that one can do. Last time I tested some off the shelf diplexers on my former employer’s VNA, I found them to have 80-90db of isolation. That’s not bad.
On Tue, Feb 11, 2020 at 7:08 AM VA3ASE via AMSAT-BB [email protected] wrote:
Good morning,
I was chatting with a friend about his experimentation with amateur satellites and have been pondering if his setup is "safe" for his radio.
He
is running an FT-847 through a duplexer (diplexer if you want to be pedantic) and into a dual-band vertical base antenna on his roof. Definitely not an ideal setup, but meant to be temporary until time and better weather allow. He has managed to make some FM contacts on AO-92
with
it.
My concern is him using a duplexer in this manner while running full duplex. I suppose this is similar to what people must do if using an Elk antenna. I just worry about there being enough isolation between the
ports
and damaging his transceiver. Are there others using similar setups or is this something to avoid?
73, Alex VA3ASE _______________________________________________ Sent via [email protected]. 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. Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. 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. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
This can be done with a pair of inexpensive du/diplexers (e.g., Comet, MFJ, etc) and a coax tee. From the antenna, on the coax to/in the shack, insert a coax tee and from the two other ports install a diplexer, one from common to VHF and the other from common to UHF (leave the other port open, or if concerned you can put a 50 Ohm load on it... I never did / had to). This has a slight mismatch, but is tolerable.
73, Jerry, K5OE
-----Original Message----- From: AMSAT-BB [email protected] On Behalf Of VA3ASE via AMSAT-BB Sent: Tuesday, February 11, 2020 7:07 AM To: AMSAT-BB [email protected] Subject: [amsat-bb] Duplexer to Dual-Band Vertical
Good morning,
I was chatting with a friend about his experimentation with amateur satellites and have been pondering if his setup is "safe" for his radio. He is running an FT-847 through a duplexer (diplexer if you want to be pedantic) and into a dual-band vertical base antenna on his roof. Definitely not an ideal setup, but meant to be temporary until time and better weather allow. He has managed to make some FM contacts on AO-92 with it.
My concern is him using a duplexer in this manner while running full duplex. I suppose this is similar to what people must do if using an Elk antenna. I just worry about there being enough isolation between the ports and damaging his transceiver. Are there others using similar setups or is this something to avoid?
73, Alex VA3ASE _______________________________________________ Sent via [email protected]. 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. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
Using duplexers like this works very well, if they are good duplexers, like the Comet. I use them all over the place as filters.
I have tested them at 80w output on 70cm with a 2m ARR Gasfet preamp ahead of a FunCube Pro + Dongle. Works perfectly and NO intermod, NO desense.
They are an ideal solution to full duplex operations at a very reasonable cost.
I have tested them on an interlaced yagi (with single feedpoint at the yagi) 5 EL on 2m, 8 EL on 70cm, fed with 65' of 1/2" hardline (duplexer in shack), as well as a pair of M2 EggBeaters 7' off the ground fed with 80' of LMR-400. Duplexers at each end.
Performance:
Usable satellite signals at -0.5 deg EL on the tower antenna. No desense, no intermod. SNR 10 dB, Q5 SSB copy both ways. Repeatable.
If that isn't ideal, I have no idea what is. 73, N0AN Hasan
On Tue, Feb 11, 2020 at 7:09 AM VA3ASE via AMSAT-BB [email protected] wrote:
Good morning,
I was chatting with a friend about his experimentation with amateur satellites and have been pondering if his setup is "safe" for his radio. He is running an FT-847 through a duplexer (diplexer if you want to be pedantic) and into a dual-band vertical base antenna on his roof. Definitely not an ideal setup, but meant to be temporary until time and better weather allow. He has managed to make some FM contacts on AO-92 with it.
My concern is him using a duplexer in this manner while running full duplex. I suppose this is similar to what people must do if using an Elk antenna. I just worry about there being enough isolation between the ports and damaging his transceiver. Are there others using similar setups or is this something to avoid?
73, Alex VA3ASE _______________________________________________ Sent via [email protected]. 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. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
There is nothing to worry about.
From the vertical with 1 coax into the shack. In the shack only 1 diplexer to split the 2m and 70cm signal, and from the diplexer's outputs to the 847's 2m and 70cm port. Allways OK!(the common connector at the diplexer is the dualband vertical one)
I worked that way for 10y but with a seperate 2m and 70cm trx, 40w both and never blew up anything. Don't use a 'T' to split the 2 bands!
73's
Jerry,ON4CJQ
----- Oorspronkelijk bericht ----- Van: "amsat-bb" [email protected] Aan: "amsat-bb" [email protected] Verzonden: Dinsdag 11 februari 2020 14:07:17 Onderwerp: [amsat-bb] Duplexer to Dual-Band Vertical
Good morning,
I was chatting with a friend about his experimentation with amateur satellites and have been pondering if his setup is "safe" for his radio. He is running an FT-847 through a duplexer (diplexer if you want to be pedantic) and into a dual-band vertical base antenna on his roof. Definitely not an ideal setup, but meant to be temporary until time and better weather allow. He has managed to make some FM contacts on AO-92 with it.
My concern is him using a duplexer in this manner while running full duplex. I suppose this is similar to what people must do if using an Elk antenna. I just worry about there being enough isolation between the ports and damaging his transceiver. Are there others using similar setups or is this something to avoid?
73, Alex VA3ASE _______________________________________________ Sent via [email protected]. 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. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb
participants (6)
-
Hasan al-Basri -
k5oe＠aol.com -
Mike Thompson -
on4cjq＠telenet.be -
Paul Stoetzer -
VA3ASE