CB SWR meter on 122Mhz?

How well do you think a CB SWR meter will work for testing the antenna
installation in an airplane?

thanks,
tom

On 2008-02-13, noman wrote:
How well do you think a CB SWR meter will work for testing the antenna
installation in an airplane?

Not worth a damn. The sensing circuitry is almost certainly not going to work
properly at VHF. A meter designed for the 2-meter ham radio band would work,
though.

What are you trying to find out? Unless something is corroded or broken,
whatever problem you have is probably not your antenna.
--
Jay Maynard, K5ZC http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
http://www.hercules-390.org (Yes, that's me!)
Buy Hercules stuff at http://www.cafepress.com/hercules-390

My radio seems to be overloaded by strong local commercial stations.
Otherwise, range and clarity are fine. I just got to wondering if my
homemade antenna or cable are a problem. To do the original install,
I used an rf field strength meter and simply adjusted the antenna
length for highest reading. It all seems to work fine, I can talk to
aircraft 40 miles away when we are both at 1000agl, but when I get
near some commercial antennas the station bleeds in and breaks the
squelch, even with it turned all the way up. I have seen this on
other rental planes, too.
tom

What are you trying to find out? Unless something is corroded or broken,
whatever problem you have is probably not your antenna.
--
Jay Maynard, K5ZC

As stated, the odds of a 27 MHz. SWR meter giving useable results on the VHF
aircraft band are slim to zero.

--
"If you think you can, or think you can't, you're right."
--Henry Ford

"noman" wrote in message
...

My radio seems to be overloaded by strong local commercial stations.

Not an unusual situation with inexpensive radios with poor front end
filtering, especially for high power FM stations at the top of the band and
at the image frequency of the radio (plus the various harmonic, crossmod,
and intermod combinations of the FM stations and your radio's
superheterodyne configuration).



Otherwise, range and clarity are fine. I just got to wondering if my
homemade antenna or cable are a problem. To do the original install,
I used an rf field strength meter and simply adjusted the antenna
length for highest reading.

That probably wasn't the cleverest way of doing it. Describe your
installation a little more, but I think I can guarantee you that it isn't
the antenna.


It all seems to work fine, I can talk to
aircraft 40 miles away when we are both at 1000agl, but when I get
near some commercial antennas the station bleeds in and breaks the
squelch, even with it turned all the way up. I have seen this on
other rental planes, too.

Then why in heaven's name would you suspect YOUR antenna if the same thing
happens to OTHER aircraft and their radios? Their antennas couldn't have
ALL failed in the same way.

On 2008-02-13, RST Engineering wrote:
"noman" wrote in message
...
Otherwise, range and clarity are fine. I just got to wondering if my
homemade antenna or cable are a problem. To do the original install,
I used an rf field strength meter and simply adjusted the antenna
length for highest reading.
That probably wasn't the cleverest way of doing it.

Maybe not the cleverest way, but it's probably good enough that it's working
fine.

Describe your installation a little more, but I think I can guarantee you
that it isn't the antenna.

I agree. This sounds like a front end overload problem. No antenna in the
world will fix that. (Well, at least not and still work for the intended
purpose.)
--
Jay Maynard, K5ZC http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
http://www.hercules-390.org (Yes, that's me!)
Buy Hercules stuff at http://www.cafepress.com/hercules-390

Tom,

I concur with Jay. You need a unit designed for the frequency being tested.

MFJ Enterprises has as series of suitable VHF SWR/Watt Meters starting at
about $40.
http://www.mfjenterprises.com/Caterg...45fc51f462651f
or
http://tinyurl.com/yo26k6

I personally use the SWR in my old RST-721 test set.

Wayne
W7ADK
http://www.soaridaho.com/



"Jay Maynard" wrote in message
...
On 2008-02-13, noman wrote:
How well do you think a CB SWR meter will work for testing the antenna
installation in an airplane?

Not worth a damn. The sensing circuitry is almost certainly not going to
work
properly at VHF. A meter designed for the 2-meter ham radio band would
work,
though.

What are you trying to find out? Unless something is corroded or broken,
whatever problem you have is probably not your antenna.
--
Jay Maynard, K5ZC http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
http://www.hercules-390.org (Yes, that's me!)
Buy Hercules stuff at http://www.cafepress.com/hercules-390

{;-)

Jim


I personally use the SWR in my old RST-721 test set.

Wayne
W7ADK
http://www.soaridaho.com/

Jim,

The RST-721 is a great little unit. In addition to tuning the antennas on
the local experimental sailplanes, I use it for my 2 meter equipment.

I didn't build one of your transceivers. I inherited the unit from a friend
who retired from soaring in his 80s.
(http://www.soaridaho.com/photogaller...k_is_Ready.jpg)

I wish aircraft tranceiver kits were still available. I enjoy building
electronics as much as working on my sailplane.
(http://www.soaridaho.com/Schreder/HP-14/N990/N990.html) I built all my
amateur radion HF equipment. (Heathkit SB-310, SB-200, SB-101 and SB640)
These old tube-based units are still running great.

Wayne
W7ADK
http://www.soaridaho.com/Schreder



"RST Engineering" wrote in message
...



{;-)

Jim


I personally use the SWR in my old RST-721 test set.

Wayne
W7ADK
http://www.soaridaho.com/

On Feb 13, 8:11*am, Jay Maynard
wrote:

Not worth a damn....

My experience runs the other way. I've tested and troubleshooted
several VHF radio antenna installations using a cheap SWR meter, and
system performance has seemed pretty uniformly inversely proportional
to the SWR reading. Of course, that's far from scientific, but it
suggests that inaccurate measurements are better than no measurements
at all.

What are you trying to find out? Unless something is corroded or broken,
whatever problem you have is probably not your antenna.

That also runs counter to my experience. Yeah, where we're talking
about classic quarter-wave whips or commercially available blade
antennas, I certainly agree. But when it comes to custom antennas,
internal antennas, copper-tape dipoles, oddly-shaped dipoles, dipole
antennas in fins and rudders, dipoles near metal parts, and carbon
fiber ground planes (all of which are common in sailplanes), radio
problems are way too often caused by the antenna or its installation.

Thanks, Bob K.
http://www.hpaircraft.com

Bob,

I played around with this a couple years ago. I trimmed an antenna using a
CB SWR to as close to 1:1 as I could get. I then measured it with my
RST-721. The '721 read 3.5:1. That is quiet a difference.

I did the same test using my quality HF SWR unit and '721 with the same
results.

Wayne
HP-14 "6F"
http://www.soaridaho.com/


"Bob Kuykendall" wrote in message
...
On Feb 13, 8:11 am, Jay Maynard
wrote:

Not worth a damn....

My experience runs the other way. I've tested and troubleshooted
several VHF radio antenna installations using a cheap SWR meter, and
system performance has seemed pretty uniformly inversely proportional
to the SWR reading. Of course, that's far from scientific, but it
suggests that inaccurate measurements are better than no measurements
at all.

What are you trying to find out? Unless something is corroded or broken,
whatever problem you have is probably not your antenna.

That also runs counter to my experience. Yeah, where we're talking
about classic quarter-wave whips or commercially available blade
antennas, I certainly agree. But when it comes to custom antennas,
internal antennas, copper-tape dipoles, oddly-shaped dipoles, dipole
antennas in fins and rudders, dipoles near metal parts, and carbon
fiber ground planes (all of which are common in sailplanes), radio
problems are way too often caused by the antenna or its installation.

Thanks, Bob K.
http://www.hpaircraft.com