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dsvs(at)ca.rr.com
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 Posted: Sat Feb 04, 2012 7:36 pm Post subject: Com and Nav Radio and Antenna Questions |
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Bob and Listers
When taking a standing wave ratio reading is it necessary to key the transmit button?
If the above is correct how does one match nav radios to coax and antennas?
I am trying to help a friend with a Pitts that has radio problems. He flew today and could not hear the attis at KWHP on the ground or in the air. The attis was functioning . Frequency 132,1
On the downwind departure leg he lost contact with the tower at less than a mile from the airport frequency 135.0
He also lost ground at the same time frequency 125.0
He was able to hear KBUR attis and tower frequencies 135.125 and 134-5 tower 118.7 even though Burbank is in a straight line with Whitman and further away.
He was able to hear KVNY attis and tower frequencies 118.45 tower 1193 and continued to hear them for at least 10 miles further away. Burkank also continued to be heard. Radio is an Icom and there have been two antennas tried a Rami bent whip mounted on the only piece of flat plate in the aircraft and an archer mounted inside the wooden turtle deck. It was suggested that the arched was having problems because of the anti UV coating on the fabric so the Rami was installed and does not seem to work any better.
Any ideas on where to start would be appreciated
Don
[quote][b]
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dsvs(at)ca.rr.com
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| Posted: Sat Feb 04, 2012 11:57 pm Post subject: Com and Nav Radio and Antenna Questions |
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| Quote: | | Additional information on the Pitts setup. The ground plane that the Rami antenna is mounted on is well under 44 by 44 inches. This aircraft is flown in acro mode and to place foil across the bottom of the fuse would cause vision problems while inverted. This is due to floor windows an either side of the existing ground plane. I believe that this is the major problem. Bob, after sending the last post I re-read the connection chapter on antennas base my belief on what I read. Comments? I am interested in the test set you talked about in the antenna chapter. Thanks in advance.Don Additional information on the Pitts setup. |
0 | Quote: | | Additional information on the Pitts setup. |
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3 | Quote: | | Additional information on the Pitts setup. |
4 | Quote: | | Additional information on the Pitts setup. |
5 | Quote: | | Additional information on the Pitts setup. |
6 | Quote: | | Additional information on the Pitts setup. |
7 | Quote: | | Additional information on the Pitts setup. |
8 | Quote: | | Additional information on the Pitts setup. |
9012
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nuckolls.bob(at)aeroelect
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| Posted: Sun Feb 05, 2012 6:26 am Post subject: Com and Nav Radio and Antenna Questions |
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At 09:31 PM 2/4/2012, you wrote:
Bob and Listers
When taking a standing wave ratio reading is it necessary to key the transmit button?
Generally, yes. Most 'stand alone' swr instruments need some
form of stimulation at the frequency of interest.
If the above is correct how does one match nav radios to coax and antennas
You find another signal source that will excite the
feedline and antenna at the frequency of interest -OR-
you use an instrument that features a built-in signal
source like . . .
[img]cid:.0[/img]
I am trying to help a friend with a Pitts that has radio problems. He flew today and could not hear the attis at KWHP on the ground or in the air.
<snip>
It was suggested that the arched was having problems because of the anti UV coating on the fabric so the Rami was installed and does not seem to work any better.
Any ideas on where to start would be appreciated
What you've described suggests a profound problem . . .
some sort of disconnect or perhaps radio failure.
Communications over distances you've suggested can
usually be covered the most rudimentary of antennas.
Certainly, an SWR test of the comm antenna AT THE
RADIO END of the feedline is indicated. Get a
hand-held transceiver and a short piece of coax
to connect it to the ship's antenna. See if communications
can be maintained on the alternate radio.
Has the ICOM been bench checked? You can ramp check
the radio by standing off a mile or so from the airplane
with a hand held. See if you can talk to each other
on the 122.750 (air-to-air, private aircraft) Unicom
frequency. Use cell phones to know that the individual
in the airplane is talking when indeed you can't hear
him on the hand-held.
| Quote: | The ground plane that the Rami antenna is mounted on is well under
44 by 44 inches. This aircraft is flown in acro mode and to place foil
across the bottom of the fuse would cause vision problems while inverted.
This is due to floor windows an either side of the existing ground
plane. I believe that this is the major problem.
|
Probably not. The size or shape of the ground
plane will not have so profound an effect on
antenna performance.
| Quote: | Bob, after sending the last post I re-read the connection chapter on
antennas base my belief on what I read. Comments? I am interested
in the test set you talked about in the antenna chapter. Thanks in
advance.
|
The MFJ-259 pictured above is the grand-daddy of
antenna analyzers. It will tell you everything you
need to know about the antenna system. Proble is,
they're kind of pricey. I think I bought my first
one about 10 years ago for under $200. They're pushing
$300 new
http://www.mfjenterprises.com/Product.php?productid=MFJ-259B
You can find them for a little less on eBay but
not much.
Another possibility is this little gem offered
on eBay and elsewhere:
http://tinyurl.com/7cl4bba
I've got one on order for evaluation. If
you don't have access to a capable VHF antenna
analyzer or swr bridge, these two options are
worth considering.
But you can do a lot with a hand-held and some
cell phones too. My guess is that the receive in
the Icom has gone to sleep . . . or the antenna
connector in the tray is open. The swr/pwr meter
test at both ends of the feedline will verify
continuity.
Bob . . .
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dsvs(at)ca.rr.com
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| Posted: Sun Feb 05, 2012 5:24 pm Post subject: Com and Nav Radio and Antenna Questions |
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From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Sunday, February 05, 2012 6:23 AM
To: aeroelectric-list(at)matronics.com
Subject: Re: Com and Nav Radio and Antenna Questions
Bob,
Thanks for the quick response.
Has the ICOM been bench checked? You can ramp check
the radio by standing off a mile or so from the airplane
with a hand held. See if you can talk to each other
on the 122.750 (air-to-air, private aircraft) Unicom
frequency. Use cell phones to know that the individual
in the airplane is talking when indeed you can't hear
him on the hand-held.
A few weeks ago we tried using a hand held with the Archer antenna and it worked fine. We sent the xcom radio in (sorry I gave the wrong name in original poat) for testing to the US dealer.
The unit is made in Australia so going back to the manufacturer is very time consuming. The dealer said everything checked out fine.
One additional item is that the radio has a remote head and no tray as the more conventional type will not fit in a Pitts
Probably not. The size or shape of the ground
plane will not have so profound an effect on
antenna performance.
Today we tried the handheld with the Archer and the Rami antennas and found the attis perfectly clear as it had been the last time we tried this. (should have known that it was not the antenna but believed the dealer when he said the radio checked out). The radio is going back to the manufacturer.
| Quote: | | Bob, after sending the last post I re-read the connection chapter onantennas base my belief on what I read. Comments? I am interestedin the test set you talked about in the antenna chapter. Thanks inadvance. |
The MFJ-259 pictured above is the grand-daddy of
antenna analyzers. It will tell you everything you
need to know about the antenna system. Proble is,
they're kind of pricey. I think I bought my first
one about 10 years ago for under $200. They're pushing
$300 new
This will not break the bank, will purchase one. It does not mention the ability to excite the feedline and antenna for setting up vor so U will need help in doing that.
The wingtip antenna you talk about in the connection is a slightly modified Archer. Archer mounts them to the fiberglass wing tip and sandwiches it between the glass and the wing root for the ground. I am looking for the instructions that came with the unit and will send them to you as soon as I find them. I would like to be able to get one of these. To work in each wing tip for my two vors. I have an APRS (2meter Jpole in one wingtip that may make it impossible to get the Archer to work.
I will ask the additional questions after I send you the Archer instructions.
Bob . . .
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Mon Feb 06, 2012 6:25 pm Post subject: Com and Nav Radio and Antenna Questions |
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At 07:20 PM 2/5/2012, you wrote:
This will not break the bank, will purchase one. It does not mention
the ability to excite the feedline and antenna for setting up vor so
U will need help in doing that.
This is a self contained antenna analyzer. It features
a variable frequency oscillator that provides a test
signal source over a 2 to 170 Mhz range. There is a
counter that displays the oscillator's present frequency.
Finally, there is an array of detectors upon which a
ratiometric analysis is conducted to deduce the resistive
and reactive components of the antenna and display them.
Instruction manual can be found here:
http://www.mfjenterprises.com/pdffiles/MFJ-259B.pdf
While not a laboratory grade instrument, it's
a lot of bang for the buck.
The wingtip antenna you talk about in the connection is a slightly
modified Archer. Archer mounts them to the fiberglass wing tip and
sandwiches it between the glass and the wing root for the ground. I
am looking for the instructions that came with the unit and will send
them to you as soon as I find them.
Yeah, Bob was a little incensed when the folks
at Van's published dimensional details on his
first RV wingtip offerings (and I repeated them
in the 'Connection). Bottom line is that the antenna
is simply a gamma-matched monopole of which there
are many variations on a theme. The now arcane
'sled runner' marker beacon antennas on the belly
are a good example.
Once you have an MFJ259 in hand, you can both
trim overall length of the Archer design to
desired center frequency, you could also adjust
the gamma-match and tuning capacitor for optimum
performance too.
While this might be an intellectually satisfying
exercise (Hams can get downright pedantic in
their quest for the Holy-SWR), it would be hard
to observe much difference in performance between
an Archer cookie-cutter installation and one that
has be tuned to technical Nirvana.
I would like to be able to get one of these. To work in each wing
tip for my two vors. I have an APRS (2meter Jpole in one wingtip
that may make it impossible to get the Archer to work.
Why a j-pole? That's an awfully big antenna for
a line-of sight application. Why not the simple
vertical whisker?
I will ask the additional questions after I send you the Archer instructions.
Got the data package. What's your question?
Bob . . .
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dsvs(at)ca.rr.com
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| Posted: Mon Feb 06, 2012 7:16 pm Post subject: Com and Nav Radio and Antenna Questions |
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I would like to be able to get one of these. To work in each wing
tip for my two vors. I have an APRS (2meter Jpole in one wingtip
that may make it impossible to get the Archer to work.
Why a j-pole? That's an awfully big antenna for
a line-of sight application. Why not the simple
vertical whisker?
Lack of room on the bottom of the AC. Most of the RV's with ATRS installed
use the JPOLE.
One Nav in the right wing with a splitter should work fine.
I will ask the additional questions after I send you the Archer
instructions.
Got the data package. What's your question?
Had to do with why the antenna needed to be as far forward as possible. I
6hink that is to keep the lighting wires that have to run forward after
going halt way up the leading edge "looking like part of the antenna". Also
why the marker beacon antennadid not drain energy to ground. Figured out
that there is no ground plane so no drain to ground.
Thanks for the help and I will let you know what the people at xcom say
about the Pitts radio. Bought the MFJ and I guess I missed the RF signal
generator in the advertisement.
Don
Bob . . .
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nuckolls.bob(at)aeroelect
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| Posted: Mon Feb 06, 2012 8:52 pm Post subject: Com and Nav Radio and Antenna Questions |
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| Quote: | Lack of room on the bottom of the AC. Most of the RV's with ATRS installed
use the JPOLE.
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But that's a 3/4 wavelength antenna. Where do you
stretch out 60" of antenna?
Bob . . .
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dsvs(at)ca.rr.com
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| Posted: Mon Feb 06, 2012 9:22 pm Post subject: Com and Nav Radio and Antenna Questions |
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But that's a 3/4 wavelength antenna. Where do you
stretch out 60" of antenna?
With a slight curve it fits in an RV wingtip. The versions that most RV'ers
are using is between 57 and 59 inches long and works fine with a continuous
bow frow front to rear.
Don
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dsvs(at)ca.rr.com
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| Posted: Mon Feb 06, 2012 9:27 pm Post subject: Com and Nav Radio and Antenna Questions |
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But that's a 3/4 wavelength antenna. Where do you
stretch out 60" of antenna?
These are the twin lead 300ohm TV cable type and the basic shape of mine is
half an elipse.
Don
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