Topband: Topband relays

[Tim Shoppa]

Continuing from N4ZR’s relay thread and Rob’s observation:

For low impedance (50 ohm ballpark) side switching, I went to Struthers Dunn (now P&B) DPDT T92 relays with paralleled 30A contacts. I got a big boy legal-limit amp and have been COMPLETELY happy with these at legal limit. Several hundred thousand QSO's through these relays without a problem. These are the "low impedance" side of my tuner switching.

Many vendors use PCB relays at legal limit “, and I’ve tried these, but I have found these to never survive legal limit RTTY contesting. They may be OK at CW or SSB duty cycles.

What I ended up using was much beefier relays. I went to Struthers Dunn (now P&B) DPDT T92 relays with paralleled 30A contacts. I got a bigger legal-limit amp and have been COMPLETEY happy with these at legal limit. Over a hundred thousand QSO's through these new relays without a problem. These are the "low impedance" side of my tuner switching.

Not relevant to my topband setup, but For the high-impedance (ladder line) side of my switching, I use open-frame relays with the contacts pried a little further apart than stock. Example part is the McMaster Carr 7384K14. N6RK outlines the process of widening the contacts in the May 2009 QST Hints and Kinks.

Tim N3QE

> On Dec 11, 2019, at 7:38 AM, Rob Atkinson <ranchorobbo at gmail.com> wrote:
> 
> Actually, if you have a quarter wave driven element and you are
> disconnecting it at the feedpoint, your relay concern shouldn't be
> voltage so much as current.   Fast switching and large contact surface
> is more important than voltage handling.
> 
> 73
> Rob
> K5UJ
> _________________
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