Today's Message Index:
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1. 01:18 AM - Re: Grounding radio antenna and transponder antenna (user9253)
2. 08:25 AM - Re: Grounding radio antenna and transponder antenna (Argonaut36)
3. 09:38 AM - Re: Re: Grounding radio antenna and transponder antenna (Robert L. Nuckolls, III)
4. 11:07 AM - Re: Grounding radio antenna and transponder antenna (user9253)
5. 01:21 PM - Daily Summary Missing? (farmrjohn)
6. 02:01 PM - Re: Daily Summary Missing? (Robert L. Nuckolls, III)
7. 02:17 PM - Re: Re: Grounding radio antenna and transponder antenna (Robert L. Nuckolls, III)
8. 02:26 PM - Re: Re: Grounding radio antenna and transponder antenna (Robert L. Nuckolls, III)
9. 07:40 PM - Re: Grounding radio antenna and transponder antenna (Argonaut36)
10. 08:48 PM - Re: Daily Summary Missing? (farmrjohn)
Message 1
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| Subject: | Re: Grounding radio antenna and transponder antenna |
Since this is a factory built aircraft, and assuming that several of this brand
and model have been built without radio problems, then maybe the problem with
your radio is not an antenna design problem. Maybe there is a problem with the
coax or its connection at either end. Would it be difficult to replace the
coax?
What are the dimensions of the metal panel used for the ground plane? Have you
removed the antenna and reinstalled it to be sure that there is a good electrical
connection to the ground plane? We are talking about a com radio antenna,
right?
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=491325#491325
Message 2
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| Subject: | Re: Grounding radio antenna and transponder antenna |
The airplane is a Pitts and Pitts are known for poor radio transmissions.
I know that I cannot get a perfect radio, I am just trying to improve on what I
have got.
The coax was replaced with a new one, made by a reputable avionics shop. That
made a difference.
The antenna (and yes, we are talking about a com antenna) was replaced with a new
one and was installed on the panel by a competent technician, paying particular
attention to getting a good electrical connection.
The dimensions of the ground plane are length 7" x width 14". The 14" width
is made up follow: central section: 6":, side sections: 4" with an angle of
15-20 degrees in relation to the central section.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=491329#491329
Message 3
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| Subject: | Re: Grounding radio antenna and transponder antenna |
At 10:24 AM 9/17/2019, you wrote:
>
>The airplane is a Pitts and Pitts are known for poor radio transmissions.
>I know that I cannot get a perfect radio, I am just trying to
>improve on what I have got.
Do you still have the old coax?
I'd like to put my hands on it . . .
The antenna (and yes, we are talking about a com antenna) was
replaced with a new one and was installed on the panel by a competent
technician, paying particular attention to getting a good electrical
connection.
Hmmm . . . vhf comm is line-of-sight
bounded with very low path losses.
Except for 'shielding' effects of surrounding
structure, satisfactory communications can
be expected with rather low power and
less-than-perfect antennas.
The dimensions of the ground plane are length 7" x width 14". The
14" width is made up follows: central section: 6":, side sections:
4" with an angle of 15-20 degrees in relation to the central section.
. . . but attached to metal airframe
components at various places around
the edges? While not an 'ideal'
ground plane it should certainly
be adequate for all but the occasional
extreme range situation while x-country.
I am just trying to establish if the radio antenna panel should also
be grounded or not and why.
If there are numerous fasteners connecting
the removable panel to metallic components
of the airframe, it's unlikely that
any additional 'grounding' will produce
observable improvement.
You have a new antenna and coax . . . are
you still experiencing unsatisfactory
performance? Have you ever had occasion
to use a hand-held radio in this
airplane?
Sorry for the run-off into the weeds.
Bob . . .
Message 4
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| Subject: | Re: Grounding radio antenna and transponder antenna |
7 x 14 inches is way too small for a ground plane if it is not attached to the
airframe on all 4 sides. So make your own ground plane. Here is a quote from
chapter 13 of Bob's book:
"VHF ground-planes can be fabricated from radial strips of copper foil, soldered
to a communing disk at the base of the antenna. Make these strips 1 wide and
trim them off 22 from the base of the vertical. 4 to 10 strips are recommended.
These may be cemented to the underside of the skin and structure. By fabricating
a commoning disk from copper, the entire assembly can be soldered."
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=491332#491332
Message 5
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| Subject: | Daily Summary Missing? |
I have not been receiving the daily posts summary by email for a while. Has that
feature been discontinued? John
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http://forums.matronics.com/viewtopic.php?p=491336#491336
Message 6
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| Subject: | Re: Daily Summary Missing? |
At 03:20 PM 9/17/2019, you wrote:
>
>I have not been receiving the daily posts summary by email for a
>while. Has that feature been discontinued? John
>
>
don't think so. try 'unsubscribing' and see
if you get the auto-responder verification
message. verify your unsubscribe request
then re-subscribe.
Bob . . .
Message 7
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| Subject: | Re: Grounding radio antenna and transponder antenna |
At 01:06 PM 9/17/2019, you wrote:
>
>7 x 14 inches is way too small for a ground plane if it is not
>attached to the airframe on all 4 sides.
While a long way from the idealized ground
plane, it's not insignificant. After all,
how much ground plane does a hand-held
transceiver have?
We're told that these aircraft have a
history of poor radio performance . . .
but they've been built in various types
and quantities for over 50 years. Given
that this is a t/c aircraft, I'm inclined
believe that the problem(s) with this
airplane may be more selective than a
poorly designed antenna installation.
We're advised that replacing the coax
made an improvement . . . and that
the antenna has been replaced with
extra attention to process. We're
not sure yet if this fixed things.
Bob . . .
Message 8
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| Subject: | Re: Grounding radio antenna and transponder antenna |
At 01:06 PM 9/17/2019, you wrote:
>
>7 x 14 inches is way too small for a ground plane if it is not
>attached to the airframe on all 4 sides.
While a long way from the idealized ground
plane, it's not insignificant. After all,
how much ground plane area does a hand-held
transceiver have?
We're told that these aircraft have a
history of poor radio performance . . .
but they've been built in various types
and quantities for over 50 years. Given
that this is a t/c aircraft, I'm inclined
to think that the problem(s) with this
airplane may be more selective than a
poorly designed antenna installation.
We're advised that replacing the coax
made an improvement . . . and that
the antenna has been replaced with
extra attention to process. We're
not sure yet if this fixed things.
Given the ease with which VHF communication
propagates between aviation facilities,
I'm inclined to believe that root cause
for unsatisfactory performance is more
profound than a soggy ground plane.
In the words of the immortal, slightly
short-circuited Number 5, "Input! Input!
I need more input!"
Bob . . .
Message 9
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| Subject: | Re: Grounding radio antenna and transponder antenna |
Thanks to both for the additional comments.
I reply to the questions of Bob as follows:
I do not have the old coax any more
I have never used a hand-held radio in this airplane
The radio performance is ok for Class D operations, but not so good for Class
B and Class C, when you need to communicate from further out and clarity of communications
is even more important
As far as additional input, I can tell you that the radio harness was replaced
without appreciable changes
I am posting a file that includes 2 pictures of my panel/antenna. The copper strips
are just taped (not soldered) and there is no communing disk. The strips
do not extend laterally, because of the limited width of the panel. I assumed
that, as we normally fly towards the radio station we are talking to, that
would be kind of acceptable.
Could you please make comments on my copper foil strips and elaborate a little
further on how the set up described by Bob is in his book could be implemented
on my panel (keeping the panel removable from the airplane)?
Note: in my previous post with the dimensions of the ground plane I have just disregarded
the copper foil strips and I have assumed that the section of panel
behind the plexigas window and the double plate work together as a ground plane.
Thanks
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=491345#491345
Attachments:
http://forums.matronics.com//files/pictures_196.pdf
Message 10
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| Subject: | Re: Daily Summary Missing? |
thanks, I'll try that. John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=491348#491348
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