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

[Chris Iwata]

Guy,

Never been on the Collins listserver

A connector is only good for RF if it makes a good connection. For AF 
use, the phono connector might be OK since impedance are high (say 10k 
ohms).  But for RF, the impedance is typically lower, so a good contact 
is more important

I hold that phono plugs with their sleeve-fit flanges don't make as good 
a connection as something screwed on (PL-259) or twisted on (BNC).  For 
males, if you bend the flanges inward every time you insert, then maybe 
they're OK.  As for the females, if you insert the male a bunch of 
times, the center wings on the female gets expanded and the contact is 
not good.  You'll have to 'pop the hood' and bend the wings back 
together.   All in all, I think phono connectors are good only for 
one-shot use.

Chris, KL7DM


On 10/9/2021 12:52 PM, Guy Giacopuzzi wrote:
>
> 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
>>>
>>> _______________________________________________
>>> Heath mailing list
>>> Heath at puck.nether.net
>>> https://puck.nether.net/mailman/listinfo/heath
>>
>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=icon> 
>> 	Virus-free. www.avast.com 
>> <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient&utm_term=link> 
>>
>>
>> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
>>
>> _______________________________________________
>> Heath mailing list
>> Heath at puck.nether.net
>> https://puck.nether.net/mailman/listinfo/heath
> -- 
>
>
> _______________________________________________
> Heath mailing list
> Heath at puck.nether.net
> https://puck.nether.net/mailman/listinfo/heath


-- 
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://puck.nether.net/pipermail/heath/attachments/20211009/b9d8ea08/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 2012email_signature.jpg
Type: image/jpeg
Size: 117949 bytes
Desc: not available
URL: <https://puck.nether.net/pipermail/heath/attachments/20211009/b9d8ea08/attachment-0001.jpg>