[amsat-bb] preamp relay question

corner5 corner5 at comcast.net
Wed Jan 21 08:11:19 PST 2009

hi all,   January 21, 2009

I am assembling my first satellite station and have a question about the 
preamp bypass relays.

 > The rig is the TS2000 and I want the flexibility to use the full RF 
range for 2m (100w) and 70cm (50w).  No RF out amp at this time.  I 
realize I may never need the upper RF power limits, but I wanted to 
build in the option from the start.
 > I have a modest antenna system with a pair of omni's each on their 
own coax feed.  Each will have its own mast mount preamp.
 > The rig is capable of inserting a sequencing Tx delay.
 > The preamp bypass relays I have on hand are: AXICOM D2n 
(V23105-A5003-A201), 12vdc coil.  I needed and found a relay with a low 
coil current (13mA) to be within the rigs trigger abilities (20mA max).  
So far so good.

 >> The relays specs. state: "switching and continuous current = 3A" and 
"maximum switching capacity = 60w, 125VA".

The question(s):
Q1... Does this stated 60w power limit for the contacts also imply a 60w 
limit for the RF level I wish to run through it?  Again, the rig limits 
out at 50w on 70cm so this is not the issue, but it (the rig) can go to 
100w on 2m.  In other words, I am unclear how the power limits of the 
contacts may or may not change as one goes from DC to 60Hz to 144 MHz to 
440 MHz?

Q2... I have been reading about relays that are specifically designed to 
handle RF, yet I see many operators that seem to use more "generic" 
relays for this purpose.  What is the requirement here with respect to 
frequency?  This station is not intended to go to GHz.

In conclusion:
_Is the above sited relay suited for this purpose?_  Are there 
constraints or design considerations?  If the answer is "nope, wont 
work", then what (and who) offers a not very expensive solution?  I 
really would like to stay under my rig's 20mA limit for the coil current 
(and therefore maintain the sequencing ability). 

And as a final comment, the general consensus seems to be to go with a 
hardwired relay system and avoid the RF switched types.  This last is 
why I am pursuing this path.

thanks for the advice! ac0z, .paul

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