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Re: Re: MFJ Relay, UHF use? (Was: Drake 2.4ghz convertor)



Hi guys,

My only concern would be if the mechanical relay is fast enough to protect 
the converter. Modern PIN diode rigs kick out RF on transmit really fast! 
That's one reason many of us use sequencing for high power/switching to give 
relays time to switch and settle before we apply RF.

For my Drake, I have inhibited xmit on the 2M IF I plan to use.

One other site to check is Greg, N0ZHE's site. He has info from Bill, W0OQC 
for the Drake. He has a protection circuit he designed.

http://www.havilandtelco.com/homepages/gregwycoff/BILL.HTM

In a message dated 10/11/00 8:51:23 AM Eastern Daylight Time, K5OE@aol.com 
writes:

> Hi Chris.
>  It is an electro-mechanical SPST relay driven by a simple rf-sense 
circuit.  
> Yes, it is probably an impedance bump, but should be of minimal concern 
since 
> it is downstream of the active circuits in receive mode; i.e., the Drake is 
> driving the coax with an amplified signal.  In fact, if you are using 50 
Ohm 
> coax, you are already at a mis-match since the Drake 2880 output is 
designed 
> for 75 Ohms.  I plan to install one right before my 2 m preamp and the 
Drake 
> unit and use the 2 m 9913F feeder to the shack.  If you wanted to avoid the 
> relay in the circuit when you are transmitting on 2 m for mode J, you could 
> put a coaxial relay in the line (ahead of the cheap relay) and have only 
the 
> Drake in the line with the cheap RF-relay.
>  73,
>  Jerry, K5OE
>  
>   "Christopher Cox" <cobox@urec.net> writes:
>  << > Bill,
>  > You are likely not the only person to need this information over the next
>  few months.  It would be nice if you could share the "fix" with the BB. 
>  For those installing these, you might want to consider using an RF-sensed
>  relay, like the Ramsey RFC-1 (http://www.ramseyelectronics.com) to switch
>  the Drake in and out.  Use the same power you run for the Drake to power
>  the relay and buy a little protection.  They cost $14.95 for the kit.
>  > 73,
>  > Jerry, K5OE
>  
>  
>  I don't know. Have you used this kit? That relay looks like a heck of an
>  impedance dimple to me. What kind of relay is it?
>  
>  Later
>  
>  Christopher Cox


73,
Mike, N1JEZ
AMSAT #29649
Local Area Coordinator
"A closed mouth gathers no feet."
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