Hi Arne,
I have to strongly disagree on the biggest problem - biggest problem is
to have good contact on receive. All the HighPower realys does not
guarantee conection below 1mA or even 10mA. Check the catalogues of ALL
the relay manufactures !
How much current you have there from 1mikroV signal into 50Ohms from the
antenna. !?!?!?!?!? On transmit the nonconducting layer which develops
on the contacts will brake through and no problem but on receive of tiny
signals ?
My experience in this field is disastrous.
The only solution are:
A: Gold plated contacts - it officially does not guarrantee good high
current but in reality no problem - in any case forget Paladium coated
contacts. They do fine on high power even they would survive
Hotswitching but you would be DEAF, that is for sure.
B: Use vacuum relay !
I bought 3-stack unit from WX0B and complained about the relays. The
answer was - YAP it is a known problem in most cases you will solve it
by hotswitching with 100-200 W about once per month - it will burn
through the contacts of the realays, he was nice to me and send me
without payment another 3 pc of realys he uses -OK they can be used to
swith some control signals but not VF for RX, they do fine for TX up to
about kW. The problem is that you find out WERY HARD that something is
wrong since there is a capacity and you still hear something you might
think the propagation is little bit worse etc. It might be also that you
just hear ecverything about 1-2S down ! It is not striking. You would
not recognize something is wrong until you make hard conection and
compare the result.
73 !
Jiri
OK1RI
ARNE GJERNING wrote:
> Not a lot of responses to my query about open frame relays but I will pass
> what info I received.
>
> 1. Use Dow Key relays (remember the 1 inch square about 3 inch long ones of
> yester year?)
>
> 2. Use vacuum relays
>
> 3. RTE24012F by Potter Brumfield
>
> 4. RKS-5DW-12 by Potte Brumfield
>
> 5. W389CX-7 by Magnecraft.
>
> If I remember correctly #4 was used by DX Engineering in their antenna
> switch boxes.
> Vacuum relays are always good ro protect contacts from weather plus other
> benefits.
>
> My use is intended to switch between antennas in a yagi stack on 10, 15, and
> 20M. Starting with 10M and I want to be VERY conservative in ratings.
> Design for 3KW+ and use at 1.5KW max ( and factor in some SWR). No hot
> switching unless I for get (I hope not).
>
> Comments/Suggestions received:
> Use DPDT and parallel contacts for higher cureent rating.
> No wx problems with vacuum relays.
> Open frame relays have immeasureable loss at HF.
> Voltage rating (insulation) is biggest concern. (1500W into 50ohms is about
> 275 volts with NO SWR)
>
> Because the W389CX-7 is rated for 1HP 600VAC motor control this may be the
> best suggrestion short of vacuum relays.
>
> Hope this info helps others with interest. If I build it they (the DX) will
> come I hope.
>
> What relays are in the highly rated RCS-8V?
>
> 73 de Arne N7KA
>
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