Topband: F fitting adaptors

[ZR]

----- Original Message ----- 
From: "Tom W8JI" <w8ji at w8ji.com>
To: "Bruce" <k1fz at myfairpoint.net>; <topband at contesting.com>
Sent: Tuesday, December 04, 2012 6:24 AM
Subject: Re: Topband: F fitting adaptors


>> When using a Ameritron remote antenna switch with SO-239 fittings, does 
>> anyone know a supplier for female F fitting to PL-259 adaptor ?
>>
>> Thanks,
>> 73
>> Bruce-K1FZ
>
> Bruce,
>
> IMO, you have the wrong switch. A transmitting type high-power switch is a 
> terrible device for receiving. The larger the relays (has a general rule) 
> the greater the problem, and it has nothing to do with sealed (enclosed) 
> or unsealed (open) relays.
>
> High current relays are very problematic when only used at low power. The 
> problem surrounds the large contact area and lack of wetting currents, and 
> no significant voltage and current ever being applied to burn through any 
> film on the contact. There are hundreds of papers by relay manufacturers 
> or others detailing this problem, and it even occurs with brand new sealed 
> or enclosed relays.
>
> The only high power relays immune to this issue are vacuum type relays.
>
> I think you are heading for long term problems with adaptors and a 
> transmitting switch.
>
> 73 Tom


While Ive experienced vacuum relays having a problem on receive a reversal 
of the coil wires took care of it, that was obviously a magnetising issue as 
has been mentioned often over the years.

OTOH the pair of Ameritron RCS-4's Id used for up to 20+ years never had an 
intermittent problem or lightning induced damage (a benefit of a big relay) 
they had somewhat poor isolation due to the daisy chain sequencing design 
and PC board layout and were replaced by a HB unit using sealed microwave 
relays. Now they wll probably blow from lightning even with the protection 
included.

I would think the Ameritron RCS-10 would be an ideal solution for a multiple 
Beverage installation as the cost is reasonable considering the 
alternatives.

Carl
KM1H