The problem is hearing the downlink. That is why the 19.5" whip is so good. It acts like a 3/4 wave antenna for the UHF downlink and it has almost >7dBi gain above 30 degrees up to over 70 degrees. So it beats a quadrifilar easily (only 4 dBi or so overhead).
As an example, my last four AO-51 passes were 36, 15, 26, and 27 degrees -max- elevation. Would you prefer gain at low to mid elevations, or above 30 degrees to work this satellite today?
A 1/4 wave will work, sometimes, but it is far from ideal for anything but occasional downlink access. As Clayton pointed out, it's easy to spot the guys on crappy antennas, as they are the ones missing calls, or transmitting on top of QSOs, because they mistake a loss of signal as a break in the action.
73, Drew KO4MA
PS My satellite grid addiction started in 2000 with a DR-605 Alinco and a 1/4 wave magmount, and a winter in the Dakotas logging production wells. UO-14, AO-27, and SO-35 were my only breaks from the boredom and snow. Since then I've operated mobile from probably 100+ grids on the FM and SSB birds both. It's addictive.
The problem is hearing the downlink. That is why the 19.5" whip is so good... and has almost 7dBi gain above 30 degrees up to over 70. So it beats a quadrifilar easily...
As an example, my last four AO-51 passes were 36, 15, 26, and 27 degrees -max- elevation. Would you prefer gain at low to mid elevations, or above 30 degrees to work this satellite today?
We need to be careful to not bring pears and pommegranets into the apples and oranges comparisons...
Were those 15 to 27 degree passes done with a Quadrifiliar on the downlink? We need to keep comparisons to apples and apples or oranges to oranges.. not all the other possibilities.
A 1/4 wave will work, sometimes, but it is far from ideal for anything but occasional downlink access.
True, It limits operation to passes above say about 25 degrees, and that does limit you to 2 or 3 passes per day, but at least they will be GOOD passes that you can hear well with smooth performance across the sky above that while mobile and with no pointing cappability. (except for a very rare direct overhead pass above 80 degrees once in a blue moon) which lasts for less than a minute..
As Clayton pointed out, it's easy to spot the guys on crappy antennas, as they are the ones missing calls, or transmitting on top of QSOs, because they mistake a loss of signal as a break in the action.
What Clayton referred to were not simple 1/4 wave verticals. He was referring to standard "mobile" antennas that have gain on the horizon and *guaranteed* nulls then between about 10 to 40 degrees (the primary satellite operating range) or so plus the small null overhead. By mentioning the fades, he was clearly referring to these standard gain antennas. By definition, a gain mobile antenna has multiple nulls between the horizon and overhead thus really playing havoc with satellitie contacts. And that is precisely why a standard mobile GAIN antenna is well known to be *no-good* for satellite work.
But this is not what a 19.5" whip does. The 1/4 (3/4) wave 19.5" whip does not have gain on the horizon (so it is rarely used for terrestrial mobile) but its pattern is ideal for satellite work on high passes. It does NOT then have a null in its pattern that causes the "crappy" contacts, and it does have plenty of gain above about 25 degrees.... and it is a smooth pattern.... not like the multi lobes of a standard mobile gain antenna.
PS My satellite grid addiction started in 2000 with a DR-605 Alinco and a 1/4 wave magmount, ... Since then I've operated mobile from probably 100+ grids on the FM and SSB birds both. It's addictive.
Yes, I think we are actually agreeing. A 1/4 wave 19.5" vertical works well. But a common mobile gain antenna *does not*. There is a big difference.
Thanks Bob, Wb4APR
Just to be fair, I have two comments on the Quadrifilar Antenna. 1. If the satellite is circular polarization the 19.5 " whip looses 3 dB of gain. 2. The common Quadrifilar Antenna is 1/2 wave 1/2 turn. The 1 wavelength, 1 turn Quadrifilar Antenna has its highest gain near or at the horizon depending on the length to diameter ratio.
Art, KC6UQH
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Bob Bruninga Sent: Wednesday, September 14, 2011 7:31 PM To: AMSAT-BB Subject: [amsat-bb] Re: Good mobile antennas to use
The problem is hearing the downlink. That is why the 19.5" whip is so good... and has almost 7dBi gain above 30 degrees up to over 70. So it beats a quadrifilar easily...
As an example, my last four AO-51 passes were 36, 15, 26, and 27 degrees -max- elevation. Would you prefer gain at low to mid elevations, or above 30 degrees to work this satellite today?
We need to be careful to not bring pears and pommegranets into the apples and oranges comparisons...
Were those 15 to 27 degree passes done with a Quadrifiliar on the downlink? We need to keep comparisons to apples and apples or oranges to oranges.. not all the other possibilities.
A 1/4 wave will work, sometimes, but it is far from ideal for anything but occasional downlink access.
True, It limits operation to passes above say about 25 degrees, and that does limit you to 2 or 3 passes per day, but at least they will be GOOD passes that you can hear well with smooth performance across the sky above that while mobile and with no pointing cappability. (except for a very rare direct overhead pass above 80 degrees once in a blue moon) which lasts for less than a minute..
As Clayton pointed out, it's easy to spot the guys on crappy antennas, as they are the ones missing calls, or transmitting on top of QSOs, because they mistake a loss of signal as a break in the action.
What Clayton referred to were not simple 1/4 wave verticals. He was referring to standard "mobile" antennas that have gain on the horizon and *guaranteed* nulls then between about 10 to 40 degrees (the primary satellite operating range) or so plus the small null overhead. By mentioning the fades, he was clearly referring to these standard gain antennas. By definition, a gain mobile antenna has multiple nulls between the horizon and overhead thus really playing havoc with satellitie contacts. And that is precisely why a standard mobile GAIN antenna is well known to be *no-good* for satellite work.
But this is not what a 19.5" whip does. The 1/4 (3/4) wave 19.5" whip does not have gain on the horizon (so it is rarely used for terrestrial mobile) but its pattern is ideal for satellite work on high passes. It does NOT then have a null in its pattern that causes the "crappy" contacts, and it does have plenty of gain above about 25 degrees.... and it is a smooth pattern.... not like the multi lobes of a standard mobile gain antenna.
PS My satellite grid addiction started in 2000 with a DR-605 Alinco and a 1/4 wave magmount, ... Since then I've operated mobile from probably 100+ grids on the FM and SSB birds both. It's addictive.
Yes, I think we are actually agreeing. A 1/4 wave 19.5" vertical works well. But a common mobile gain antenna *does not*. There is a big difference.
Thanks Bob, Wb4APR _______________________________________________ Sent via AMSAT-BB@amsat.org. 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
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<snip> But this is not what a 19.5" whip does. The 1/4 (3/4) wave 19.5" whip does not have gain on the horizon (so it is rarely used for terrestrial mobile) but its pattern is ideal for satellite work on high passes. It does NOT then have a null in its pattern that causes the "crappy" contacts, and it does have plenty of gain above about 25 degrees.... and it is a smooth pattern.... not like the multi lobes of a standard mobile gain antenna. </snip>
Hi Bob,
This is off topic and didn't want to start something on the list... :), but can I convert my current magmount gain antenna simply by replacing the whip or is the "gain" stuff in the magmount itself? If so, would any thin steel rod do? I'd really like to give this a try!
73's Peter VE7NGP
Peter, I donno. The only 1/4 19.5" antenna I ever used I just drilled into the roof above the dome light and installed an NMO mount and simple whip. For conversion of an existing mount, if it is a 5/8's wave vertical (most mobiles are) then there is a matching network in the base.
The little tiny micro whips are ideal, but most of them now are being made as "dual band" which then destroys their 7 dBi gain above the horizon.
No easy answers here. Bob
-----Original Message----- From: Ng, Peter [mailto:Peter.Ng@bccdc.ca] Sent: Thursday, September 15, 2011 12:47 PM To: 'Bob Bruninga '; AMSAT-BB Subject: RE: [amsat-bb] Re: Good mobile antennas to use
<snip> But this is not what a 19.5" whip does. The 1/4 (3/4) wave 19.5" whip does not have gain on the horizon (so it is rarely used for terrestrial mobile) but its pattern is ideal for satellite work on high passes. It does NOT then have a null in its pattern that causes the "crappy" contacts, and it does have plenty of gain above about 25 degrees.... and it is a smooth pattern.... not like the multi lobes of a standard mobile gain antenna. </snip>
Hi Bob,
This is off topic and didn't want to start something on the list... :), but can I convert my current magmount gain antenna simply by replacing the whip or is the "gain" stuff in the magmount itself? If so, would any thin steel rod do? I'd really like to give this a try!
73's Peter VE7NGP
Thanks for the plots Bob. The 2m havewave appears to do well on 70cm above 30 degrees, and fairly poor below that elevation. The 70cm 1/4 wave appears to suffer from no real nulls except at the very high elevations. It is about 5 DB down from the 2m 1/4 wave, but is also much more usable on the below 30 degree passes.
So, would a dualband that is 1/4 wave on each band cover things pretty well? It appears like it would.
73s John AA5JG
On Thu, Sep 15, 2011 at 12:07 PM, Bob Bruninga bruninga@usna.edu wrote:
Peter, I donno. The only 1/4 19.5" antenna I ever used I just drilled into the roof above the dome light and installed an NMO mount and simple whip. For conversion of an existing mount, if it is a 5/8's wave vertical (most mobiles are) then there is a matching network in the base.
The little tiny micro whips are ideal, but most of them now are being made as "dual band" which then destroys their 7 dBi gain above the horizon.
No easy answers here. Bob
-----Original Message----- From: Ng, Peter [mailto:Peter.Ng@bccdc.ca] Sent: Thursday, September 15, 2011 12:47 PM To: 'Bob Bruninga '; AMSAT-BB Subject: RE: [amsat-bb] Re: Good mobile antennas to use
<snip> But this is not what a 19.5" whip does. The 1/4 (3/4) wave 19.5" whip does not have gain on the horizon (so it is rarely used for terrestrial mobile) but its pattern is ideal for satellite work on high passes. It does NOT then have a null in its pattern that causes the "crappy" contacts, and it does have plenty of gain above about 25 degrees.... and it is a smooth pattern.... not like the multi lobes of a standard mobile gain antenna. </snip>
Hi Bob,
This is off topic and didn't want to start something on the list... :), but can I convert my current magmount gain antenna simply by replacing the whip or is the "gain" stuff in the magmount itself? If so, would any thin steel rod do? I'd really like to give this a try!
73's Peter VE7NGP
Sent via AMSAT-BB@amsat.org. 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 (5)
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Andrew Glasbrenner -
Art McBride -
Bob Bruninga -
John Geiger -
Ng, Peter