[MRCA] BC-654 Antenna challenge
Al Klase
ark at ar88.net
Sun Jan 21 15:07:26 EST 2018
Mark,
On 1/21/2018 2:18 PM, mkdorney at aol.com wrote:
> Hello Mr. Klase,
> I have an extra AN-160 long wire antenna that was normally issued
> with the BC-1306. When set up, this antenna looks like an inverted L
> antenna, and it works on 80 meters. I can make the antenna in the
> BC-654 manual, but if the AN-160 will work with the BC-654, why
> re-invent the wheel? Would this antenna work better than commo wire?
>
With all the jumpers in, the AN-160 in about a half-wave at the upper
end of 75-meter. Perfect! The only issue is whether the BC-654 will
load it properly. I suspect it will be ok. Throw out 20-30 feet of
counterpoise, on the ground, connected to the ground terminal. The T
(Windom) might be a better match, but you'll have to judge that
yourself. One of the advantages of the end-fed half is that you can get
away with only one support in the middle. 10 feet off the ground works
just fine for NVIS,
> Jeez, when I was with the US 10th Mountain Division in the 1990's,
> each of my forward observers had to have a long wire antenna made up
> of a single strand of commo wire, using the plastic spoon from an MRE
> as an insulator, to use with our PRC-77 radios to give each of them an
> antenna that was directional in order to make it harder to DF their
> Forward Observation Posts. What you describe sounds like the same
> thing. I do wonder how this antenna helps eliminate the skip zone though.
The term long wire gets abused a lot, even in Army TM's. A long wire is
multiple whole wavelengths long. You field expedient PRC-77 antenna was
a/bona-fide/ long wire. An end-fed half-wave is not. If it's not cut
to a particular frequency, let's call it a random wire.
>
> The AN-2259 is a far more complicated antenna to build, and takes
> up much more room when set up. I am looking to make contact with a
> station some 80 to 100 miles from my station, which will be using a
> BC-654-A
For our purposes the AN-2259 is a complete boondoggle. It's primary
advantage is you don't have to adjust the antenna to cover multiple
bands. I use a simplified AN-160 with just two jumpers, to cover 75,
60, and 40 meters.
>
> Mark
> WW2RDO
We've demonstrate all of this over and over in 15+ years of MRCA field
operations.
VY 73,
Al
>
> In a message dated 1/21/2018 1:57:24 PM Eastern Standard Time,
> ark at ar88.net writes:
>
> Mark,
>
> *Commo wire!!!*
>
> NVIS antennas are generally what half-assed hams had been doing
> since being banned to 200-meter and down. A low half-wave wire
> will get you a lot of high angle radiation.
>
> The vertical antennas on WWII HF gear were really only appropriate
> for "direct wave" communication, say 10-20 miles. And, they were
> woefully inefficient, being only a small fraction of a wavelength
> in height. When you were sitting still, you threw some wire in a
> tree for better results.
>
> http://www.mrca.ar88.net/Old%20Pages/Net/Images/Dipole%20vs.%20Whip.png
>
> So, What's Wrong with My Whip?
> Your signal is shown in red. (Low half-wave in blue.)
>
> The SCR-284 TM shows a "T-Shaped Antenna." (That's a Windom)
>
>
>
> Of course, one of the big problems for useful, 24-hour NVIS is
> that the early portable sets were all stuck on one band around
> 5000KHz. This explains why the the SCR-694 / BC-1306 (3.8-6.5
> MHz) was being replace by the AN/GRC-9 (2-12 MHZ) as the war drew
> to a close. Both radios came with end-fed half wave antennas in
> addition to whips.
>
> Enough from me!
> Al
>
> On 1/21/2018 11:35 AM, WW2RDO via MRCA wrote:
>
> I know that the American, British and German Army first
> started using NVIS antennas for some of their HF radios during
> World War Two. So far, I'm having trouble finding much
> information about how far each military went as far as NVIS
> antenna use, or any photos of any WW2 vintage antenna.
>
> So here's what I'm trying to build. I'm looking to build an
> NVIS antenna for the BC-654 using only material available
> during WW2. That would include any balun or any additional
> antenna tuner to be used with the radio, if they are needed.
> I am unaware of any issue NVIS antenna issued for the BC-654.
> Particularly concerning is the fact that the BC-654 did not
> use coaxial feed line for the antenna. I know the AN/GRC106
> had an NVIS antenna, the AS-2259GR , but I see that the
> AN/GRC106 used a coax antenna feed line. I am not sure that
> the AS-2259GR antenna, even if I could find one, would work
> with a BC-654.
>
>
> Mark D.
>
>
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> --
> Al Klase – N3FRQ
> Jersey City, NJ
> http://www.skywaves.ar88.net/
>
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--
Al Klase – N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/
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