[Heath] Heathkit SB-644A, Remote VFO Cables

[Guy Giacopuzzi]

Chris,

I thought we had a discussion about RCA connectors on the Collins 
listserve; I thought the consensus was that RF wise, they were 
fabulous.  The main issue is the females wear out, and getting good ones 
to replace the ones you have is a bit of a problem now...am I wrong?

Guy

...one of the hams at Heath...

> Heathkit back then used phono connectors a lot, probably because they 
> were cheap. They are not the best connectors to use for RF.  The 
> sleeve-fit ground makes for lousy connections.
>
> Since the coax cables are not carrying any appreciable power, just 
> about any well-shielded cable will work.  The impedance is not an 
> issue for anything less than say 6 feet. The reason for the coax is to 
> keep the RF isolated, not to match anything. Don't use audio coax 
> cable simply because the shielding is not very good.
>
> RG-8X is pretty thick and stiff.  It will work but be cumbersome, plus 
> you'll have a helluva time trying to solder on the phono plugs.  If 
> you're still worried about impedance, use RG-58
>
> One of the major drawbacks of the SB104 is that it lacked RIT 
> (receiver incremental tuning) and XIT.  To have a separate VFO just to 
> accomplish this simple feature is overkill.   I built RIT/XIT into my 
> much older HW-101 (similar solid state VFO) pretty easily with a 
> varactor, a pot, and some switching circuitry.
>
> Chris, KL7DM
>
> On 10/8/2021 2:54 PM, Steven Feinsmith wrote:
>> I acquired Heathkit Ham radio and worked on my technician and general 
>> exams to earn the callsign soon.
>>
>> I cleaned my SB-644A, Remote VFO, and checked everything to ensure it 
>> was in good working order. I have a pair of shielded coaxial cables 
>> to link with my Heathkit SB-104A transceiver. Both ends use RCA male 
>> phono connectors. I realized they were short, a foot long. They 
>> cannot reach the remote VFO unless I have put them on the left 
>> instead of the right. I checked the assembly manual, and it showed 
>> that #343-3, a large, coaxial cable, came 4 feet long. It has cut to 
>> 2 feet long instead of one foot long. I decided to get a new coaxial 
>> cable. The original cable labeled as follows:
>>
>> 300V  80 degree  FR-1  (UL)  AWN  STYLE  1436
>>
>> I searched for the specification for that cable. Unfortunately, there 
>> was almost no information such as 50-ohms? I called three different 
>> vendors, and they did not know much about it. I think I can use RG-8x 
>> coaxial cable, but I am not sure if this kind of cable can be 
>> attached with an RCA male connector? What is your suggestion?
>>
>> 73,
>> Steven
>>
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