I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the ARRL Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of a 15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34]
the helix is a nice antenna...however...once wound for either RHCP or LHCP there's no going back. So switching from R to L or L to R is out of the question. Unless of course the chosen polarity is always compatible with the satellite in use. Unless you have L and a R helix and switch between them, that can get a "little" involved. Many times it is very convenient to be able to switch between L or R during a pass, at times it can make the contact happen. This is of course is easy with a L/R CP yagi. I have used a helix for L band (1.2ghz ) as well as feeds for a 2.4ghz dish. They are a fine antenna with a fair amount of bandwidth. For a 16+ turn helix I have used stainless steel "U" channel for the center support. If Clair, VE3NPC is listening, he's the resident helix guy. Just my opinion, your mileage may differ. 73 Bob W7LRD Seattle
----- Original Message ----- From: "Rolf Krogstad" [email protected] To: [email protected] Sent: Monday, May 13, 2013 9:22:57 AM Subject: [amsat-bb] Helical Antenna on 70 cm
I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the ARRL Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of a 15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34] _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Thanks, Bob.
Is there a commercial yagi available for 435 MHz which is R-L switchable?
Rolf NR0T
On Mon, May 13, 2013 at 8:21 PM, Bob- W7LRD [email protected] wrote:
the helix is a nice antenna...however...once wound for either RHCP or LHCP there's no going back. So switching from R to L or L to R is out of the question. Unless of course the chosen polarity is always compatible with the satellite in use. Unless you have L and a R helix and switch between them, that can get a "little" involved. Many times it is very convenient to be able to switch between L or R during a pass, at times it can make the contact happen. This is of course is easy with a L/R CP yagi. I have used a helix for L band (1.2ghz ) as well as feeds for a 2.4ghz dish. They are a fine antenna with a fair amount of bandwidth. For a 16+ turn helix I have used stainless steel "U" channel for the center support. If Clair, VE3NPC is listening, he's the resident helix guy. Just my opinion, your mileage may differ. 73 Bob W7LRD Seattle
*From: *"Rolf Krogstad" [email protected] *To: *[email protected] *Sent: *Monday, May 13, 2013 9:22:57 AM *Subject: *[amsat-bb] Helical Antenna on 70 cm
I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the ARRL Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of a 15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34] _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Rolf,
I don't believe that's possible. It would be like asking for a screw that can be turned in either direction. L / R switching is done by switching between two antennas.
Greg KO6TH
Rolf Krogstad wrote:
Thanks, Bob.
Is there a commercial yagi available for 435 MHz which is R-L switchable?
Rolf NR0T
On Mon, May 13, 2013 at 8:21 PM, Bob- W7LRD[email protected] wrote:
the helix is a nice antenna...however...once wound for either RHCP or LHCP there's no going back. So switching from R to L or L to R is out of the question. Unless of course the chosen polarity is always compatible with the satellite in use. Unless you have L and a R helix and switch between them, that can get a "little" involved. Many times it is very convenient to be able to switch between L or R during a pass, at times it can make the contact happen. This is of course is easy with a L/R CP yagi. I have used a helix for L band (1.2ghz ) as well as feeds for a 2.4ghz dish. They are a fine antenna with a fair amount of bandwidth. For a 16+ turn helix I have used stainless steel "U" channel for the center support. If Clair, VE3NPC is listening, he's the resident helix guy. Just my opinion, your mileage may differ. 73 Bob W7LRD Seattle
*From: *"Rolf Krogstad"[email protected] *To: *[email protected] *Sent: *Monday, May 13, 2013 9:22:57 AM *Subject: *[amsat-bb] Helical Antenna on 70 cm
I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the ARRL Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of a 15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34] _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
M2 makes one, and I think Gulf Alpha antennas has one.
73, Jim KQ6EA
On 05/14/2013 02:04 AM, Rolf Krogstad wrote:
Thanks, Bob.
Is there a commercial yagi available for 435 MHz which is R-L switchable?
Rolf NR0T
On Mon, May 13, 2013 at 8:21 PM, Bob- W7LRD [email protected] wrote:
the helix is a nice antenna...however...once wound for either RHCP or LHCP there's no going back. So switching from R to L or L to R is out of the question. Unless of course the chosen polarity is always compatible with the satellite in use. Unless you have L and a R helix and switch between them, that can get a "little" involved. Many times it is very convenient to be able to switch between L or R during a pass, at times it can make the contact happen. This is of course is easy with a L/R CP yagi. I have used a helix for L band (1.2ghz ) as well as feeds for a 2.4ghz dish. They are a fine antenna with a fair amount of bandwidth. For a 16+ turn helix I have used stainless steel "U" channel for the center support. If Clair, VE3NPC is listening, he's the resident helix guy. Just my opinion, your mileage may differ. 73 Bob W7LRD Seattle
*From: *"Rolf Krogstad" [email protected] *To: *[email protected] *Sent: *Monday, May 13, 2013 9:22:57 AM *Subject: *[amsat-bb] Helical Antenna on 70 cm
I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the ARRL Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of a 15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34] _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Rolf, NR0T
The KLM has the model 435-40CX crossed yagi i.e. a 20+20 crossed elements complete with a on board switching relay and phasing harness to get RHCP or LHCP from the shack
Since the above model is relatively old I don't know if you can get one of it actually in USA but the KLM now M2 produces similar models with better performance.
I have a 435-40CX still available on market in Italy at convenient and reduced price and it works very well.
Just for experimentation I have modified and upgraded this antenna to get four polarizations H-V-RHCP-LHCP on switching from the shack using four small coax relays and phasing harness on board of the antenna.
You can see this modifications reading my articles " Switching four Polarization on a 70 cm Crossed Yagi" published by the AMSAT Journal March/April 2007 Part-1 and May/June 2007 Part-2
Have fun !
73" de
i8CVS Domenico
----- Original Message ----- From: "Rolf Krogstad" [email protected] To: "Bob- W7LRD" [email protected] Cc: [email protected] Sent: Tuesday, May 14, 2013 4:04 AM Subject: [amsat-bb] Re: Helical Antenna on 70 cm
Thanks, Bob.
Is there a commercial yagi available for 435 MHz which is R-L switchable?
Rolf NR0T
On Mon, May 13, 2013 at 8:21 PM, Bob- W7LRD [email protected] wrote:
the helix is a nice antenna...however...once wound for either RHCP or LHCP there's no going back. So switching from R to L or L to R is out of the question. Unless of course the chosen polarity is always compatible with the satellite in use. Unless you have L and a R helix and switch between them, that can get a "little" involved. Many times it is very convenient to be able to switch between L or R during a pass, at times it can make the contact happen. This is of course is easy with a L/R CP yagi. I have used a helix for L band (1.2ghz ) as well as feeds for a 2.4ghz dish. They are a fine antenna with a fair amount of bandwidth. For a 16+ turn helix I have used stainless steel "U" channel for the center support. If Clair, VE3NPC is listening, he's the resident helix guy. Just my opinion, your mileage may differ. 73 Bob W7LRD Seattle
*From: *"Rolf Krogstad" [email protected] *To: *[email protected] *Sent: *Monday, May 13, 2013 9:22:57 AM *Subject: *[amsat-bb] Helical Antenna on 70 cm
I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the ARRL Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of a 15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34] _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Rolf,
My understanding is that the material used for center pole in a helix doesn't affect the antenna dimensions or performance much at all. So, feel free to use whatever material you have handy that will work mechanically and environmentally (e.g. ice load and sun exposure). I've never made a helix for 70cm, but that's about a low a frequency as I'd consider. They get kind of large and unwieldy as you go down in frequency, and a 6" coil on a 7' boom would be pushing it for me. A crossed yagi could be mechanically easier to build, and, to Bob's point, you could make it run either polarity.
Good luck,
Greg KO6TH
Rolf Krogstad wrote:
I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the ARRL Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of a 15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34] _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Rolf, NR0T
The fiberglass rods made of "Isophthlic Polyester Resin" is a good choice of material at UHF frequencies and it is the material I have used for my RHCP 10 turns Helical Antenna for 435 MHz in use on the roof since 1976 beginning from OSCAR-8 Mode-J and actually working since than for VO-52
In a separate email I have sent to you a zipped file with all mechanical drawings to built it in all details.If you like to increase the numbar of turns from 10 to 15 no problems because the only adjustement required is to change a little bit step by step the distance between the reflector and the first turn in order to get the lower possible VSWR.
In my Helical Antenna the boom is a very hard plastic tube called Moplen, outside diameter 42 mm ,inside diameter 34 mm and so 5,5 mm thick.
The turns of the Helical are made with 8 mm diameter solid annealed aluminum rod and the spacers between the turns are 8 mm outside diameter fiber glass rods.
For best performance I have mounted the supporting steel horizontal harm on the rear of reflector in order to prevent interactions between the EM field of the turns and the mechanical metallic support.
In order to balance the weight of the Antenna I have mounted in the rear of reflector a round counterweight made of lead.
Have fun !
73" de
i8CVS Domenico
----- Original Message ----- From: "Rolf Krogstad" [email protected] To: [email protected] Sent: Monday, May 13, 2013 6:22 PM Subject: [amsat-bb] Helical Antenna on 70 cm
I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the
ARRL
Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of
a
15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34] _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
A good source of antennas and antenna advice is Dave W6OAL
He likes Loop yagis for 23cm
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Rolf Krogstad Sent: Monday, May 13, 2013 10:23 AM To: [email protected] Subject: [amsat-bb] Helical Antenna on 70 cm
I am new to satellites and new to the design requirements for UHF and am looking for advice.
I am looking to build a Helical antenna for the 70cm Band. I am considering the plans for such an antenna from the 2010 edition of the ARRL Satellite Handbook. The plans call for a 235 cm (7' 8") long, 2.5 cm (1") diameter center support made of either a wooden dowel which has been treated or a fiberglass tube. It also requires multiple 7.6 cm (3") spacers for the helical element.
My question is would fiberglass rods made of "Isophthlic Polyester Resin" be a good choice of material at UHF frequencies? I hesitate to use treated wood because I plan to mount this on the top of a 15 meter high tower and it isn't very accessible.
Thanks
Rolf NR0T [EN34] _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
participants (6)
-
Bob- W7LRD -
Dave WØDHB -
Greg D -
i8cvs -
Jim Jerzycke -
Rolf Krogstad