[Milsurplus] Cmd set rec ant mod

[Al Klase]

Larry,

The circuit was obviously laid out to support a short (read 
high-impedance) antenna.  ( Like from the cockpit to the tail.)  The 
suggested mod. will likely improve the situation.

But, my preference would be to keep the radio unmodified, and feed it 
from the coax with a broad-band step up transformer.  A 1:9 (1:3 turns 
ratio) or even 1:16 (1:4 turns) unbalanced to unbalanced autotransformer 
is pretty easy to build, once you've broken down and bought some 
appropriate ferrite cores.  You'll find other uses for them.

See my 1:9 un-un here; http://www.skywaves.ar88.net/ANTENNA/N3FRQ_Baluns.pdf

Regards,
Al


On 8/22/2013 9:25 PM, telegrapher at q.com wrote:
>
>
> Letters to the Editor, Page 14.
>
> Text quoted " The following method of connecting coaxial lines into a command receiver has resulted in an increase of sensitivity of from 3-5 db and on a 3-6 mc BC-454 used on an original frequency."
>
> Most articles on conversion of command equipment merely suggest the substitution of a coaxial connector tof the original antenna binding post, but a tremoundous loss of sensitivity was noted when using low impedance feed lines.
>
> (attached simple schematic)
>
> What the gentleman suggests is to remove the original series condenser from the antenna post and a .01 ufd connected from the antenna input to the terminal on the antenna coil socket that is grounded to the condenser frame.  At the same time remove the solid tinned ground wire and put a .001ufd disc ceramic in series to ground.
>
> Whatcha tink Geno?
>
> W2JCI was the gentleman who suggested this change.  Anyone do such a thing?
>
> Lotta neat stuff back then to improvise.  Things that many of the newer hams have lost over the years.
> Larry
> W0OGH
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/