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nuckolls.bob(at)aeroelect
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 Posted: Sat Jan 21, 2012 2:44 pm Post subject: SWR Meter OOPS |
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Sorry, hit the 'send' function before finishing the
reply. Ignore the previous posting . . .
At 12:57 PM 1/21/2012, ROGER & JEAN CURTIS wrote:
| Quote: | I have a Vintage Sears SWR / FS meter which appears to be
the same as the Cal Com Model 9856. Can this be used to check the antenna
on aircraft nav com radios? If so, how do I set it up for use?
Roger
|
This is no doubt an excellent example of a
directional coupler sampling reflectometer. Dozens
of products of this genre' were manufactured
and they are quite common.
[img]cid:.0[/img]
A general description of this device can be secured
at:
http://en.wikipedia.org/wiki/SWR_meter
They are quite effective over the range of 2 to
perhaps 30 MHz. To be useful, the length of transmission
line inside must be a small fraction of a wavelength
at the frequency of interest. In this case, 126 Mhz.
When you study the design of a Watt/SWR meter suited
for VHF . . .
[img]cid:.1[/img]
The sampling is in a single "slug" that can be
rotated to present complimentary forward and reverse
power samples.
[img]cid:.2[/img]
The slug contains a miniaturized version of the directional
coupler sampling sampling loops found in your SWR meter.
Here's a photo of a miniaturized version of your SWR meter
optimized for VHF/UHF service. The loops are about 1/2"
long.
[img]cid:.3[/img]
So the short answer is the instrument you have is useful
at Citizen's band frequencies and below. You need something
tailored to VHF to do any serious work with your ship's
antennas. Something like this
[img]cid:.4[/img]
which can be had for about $60 off eBay. It's optimized
for VHF and will produce more useful readings.
For an more in-dept explanation you can browse a compendium of
publications at:
http://www.aeroelectric.com/articles/RF_PWR_Meter/
and in particular an article at:
http://www.aeroelectric.com/articles/RF_PWR_Meter/Directional%20Coupler%20pa0nhc.pdf
which describes a modification of instruments like yours
that extends their useful range into VHF/UHF regions.
Bob . . .
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rlborger(at)mac.com
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| Posted: Sun Jan 22, 2012 6:10 am Post subject: SWR Meter OOPS |
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Bob,
WRT the SW DIGITAL SWR METER shown below.
It looks like a pretty cool little device that anyone could have in their OBAM tool kit. And there are sure bunches of them for sale on e-bay.
It appears to have threaded (TNC?) connections. Would one make up short lengths of BNC to TNC coax to connect it into the antenna line? Or are there BNC/TNC adaptors that are more appropriate?
Blue skies & tailwinds,
Bob Borger
Europa XS Tri, Rotax 914, Airmaster C/S Prop.
Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP
3705 Lynchburg Dr.
Corinth, TX 76208-5331
Cel: 817-992-1117
rlborger(at)mac.com (rlborger(at)mac.com)
On Jan 21, 2012, at 4:41 PM, Robert L. Nuckolls, III wrote:
| Quote: | You need something
tailored to VHF to do any serious work with your ship's
antennas. Something like this
[img]cid:D87DF57A-0F9C-4513-A475-22ACE53A2A93[/img]
which can be had for about $60 off eBay. It's optimized
for VHF and will produce more useful readings.
|
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mrspudandcompany(at)veriz
Guest
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| Posted: Sun Jan 22, 2012 7:41 am Post subject: SWR Meter OOPS |
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You need something
tailored to VHF to do any serious work with your ship's
antennas. Something like this
which can be had for about $60 off eBay. It's optimized
for VHF and will produce more useful readings.
I noticed on Ebay that these come in
several different flavors, various power output, and some specific to a
particular radio.
For our OBAM purpose, are there any specs to
adhere to, other than VHF band?
Thanks,
Roger
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nuckolls.bob(at)aeroelect
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| Posted: Sun Jan 22, 2012 7:46 am Post subject: SWR Meter OOPS |
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At 08:06 AM 1/22/2012, you wrote:
| Quote: | Bob,
WRT the SW DIGITAL SWR METER shown below.
It looks like a pretty cool little device that anyone could have in their OBAM tool kit. And there are sure bunches of them for sale on e-bay.
It appears to have threaded (TNC?) connections. Would one make up short lengths of BNC to TNC coax to connect it into the antenna line? Or are there BNC/TNC adaptors that are more appropriate? |
Those are type N connectors. You'll want some
N-male/BNC-female adapters to make the transition
to connectors popular with the aircraft world.
[img]cid:.0[/img]
I have a Bird 43 and don't need one of these for
my own purposes but I would like to put my hands
on one to compare with the Bird. As a teacher
it is always good to be able to say, "been there,
done that."
So Roger my friend, here's a plan. I'll order
one of these along with the requisite adapters.
I'll fabricate a BNC-BNC jumper cable that facilitates
the insertion of the instrument into your transmitter's
coax feeder. I'll compare the device with my
Bird 43 and report the findings to the List.
Then I'll offer you the test article and
accessories for what I have in them + postage.
Sounds like a deal to me . . . what say you sir?
Bob . . .
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mrspudandcompany(at)veriz
Guest
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| Posted: Sun Jan 22, 2012 8:46 am Post subject: SWR Meter OOPS |
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So Roger my friend, here's a plan. I'll order
one of these along with the requisite adapters.
I'll fabricate a BNC-BNC jumper cable that facilitates
the insertion of the instrument into your transmitter's
coax feeder. I'll compare the device with my
Bird 43 and report the findings to the List.
Then I'll offer you the test article and
accessories for what I have in them + postage.
Sounds like a deal to me . . . what say you sir?
Bob . . .
Sounds like a deal to me, go for it.
When everything is complete you can package
it up with the gooseneck light and ship it all together. I'm not in a rush,
so if you can do it in the next 3 or 4 months, that would be great.
Roger
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rlborger(at)mac.com
Guest
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| Posted: Sun Jan 22, 2012 8:52 am Post subject: SWR Meter OOPS |
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Bob,
You got a deal!
Let me know how much when you are ready to ship and I'll have a check in the mail that day.
Blue skies & tailwinds,
Bob Borger
Europa XS Tri, Rotax 914, Airmaster C/S Prop.
Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP
3705 Lynchburg Dr.
Corinth, TX 76208-5331
Cel: 817-992-1117
rlborger(at)mac.com (rlborger(at)mac.com)
On Jan 22, 2012, at 9:36 AM, Robert L. Nuckolls, III wrote:
| Quote: | At 08:06 AM 1/22/2012, you wrote:
| Quote: | Bob,
WRT the SW DIGITAL SWR METER shown below.
It looks like a pretty cool little device that anyone could have in their OBAM tool kit. And there are sure bunches of them for sale on e-bay.
It appears to have threaded (TNC?) connections. Would one make up short lengths of BNC to TNC coax to connect it into the antenna line? Or are there BNC/TNC adaptors that are more appropriate? |
Those are type N connectors. You'll want some
N-male/BNC-female adapters to make the transition
to connectors popular with the aircraft world.
<15f453f4.jpg>
I have a Bird 43 and don't need one of these for
my own purposes but I would like to put my hands
on one to compare with the Bird. As a teacher
it is always good to be able to say, "been there,
done that."
So Roger my friend, here's a plan. I'll order
one of these along with the requisite adapters.
I'll fabricate a BNC-BNC jumper cable that facilitates
the insertion of the instrument into your transmitter's
coax feeder. I'll compare the device with my
Bird 43 and report the findings to the List.
Then I'll offer you the test article and
accessories for what I have in them + postage.
Sounds like a deal to me . . . what say you sir?
Bob . . .
|
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sun Jan 22, 2012 10:00 am Post subject: SWR Meter OOPS |
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| Quote: | Sounds like a deal to me, go for it.
|
It shall be done.
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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