[ARC5] " ARC-5 " Transmitter Antenna Matching.

[zeno]

I looked this up. It is (chapter 19.16/ Transmission Lines) in my 
ARRL handbook. In figure 19.14 they show a "4::1 Balanced to Balanced 
current transformer wound on two cores, which are separated. Use 12 
bifilar turns of #14 enameled wire wound on FT240-43 cores for A and 
B. Distribute bifilar turns evenly around core."

OK, sounds do-able. Where do you get these FGT240-43  cores, is this 
something readily available? They only show an abstract illustration. 
As a beginning do-it-yourself hobbyist a step by step photo would be 
nice, but I will have to use my imagination as my elmer.... they 
don't really show how to actually do it, are these two cores just 
hanging in mid-air or can they be mounted on the same whatever? Is 
the proximity of the two cores critical. This is always the problem 
with these abstract illustrations. You cannot really do these 
projects without specific knowledge, if you have no other experience. 
The handbook, and almost all other references take this same 
approach, eg. only abstract illustrations or schematics, never an 
illustration of what a typical solution actually looks like. Very 
frustrating. It says the "cores or separated", what does that mean, 
inches or miles? Ok, I have concluded that the handbook is virtually 
useless, even though it appears to have "information".....


Bill




>(per request)
>
>On Loading an Antenna:
>
>The SCR-274N and AN/ARC-5 radios were not designed
>to load a 50 ohm antenna. They were intended for
>antennas of about 5-12 ohms. In order to load
>a 50-ohmer you'll need to do one of two things:
>
>Cheap and easy- put a good quality NP0 (no thermal drift)
>capacitor of at least 1000 volts between the antenna terminal
>and the coax center conductor (in series).
>For 40 meters, use 50 PF. For 80 meters, use 75 PF.
>Non-NP0 caps may heat, drift and cause chirp.
>
>More trouble but better:
>Wind a 4:1 "UNUN," which is an unbalanced to unbalanced balun,
>and use it at the antenna connector to match the coax.
>The design is available in the Handbook.
>Will cost a couple of watts but worth it.
>
>I hope these tips will be of value to you.
>
>Good Luck with it!
>
>73 DE Dave Stinson AB5S
>arc5 at ix.netcom.com

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