[Mich VHF UHF Society] 28 VDC Type N coax relay for sale

Roger Cox rgcox2 at gmail.com
Wed Sep 24 19:55:37 CDT 2014


I saw this one on eBay and it looked like the kind I wanted - similar to 
the Dow Key Microwave 402-series.  However, they didn't post many 
details about it - just that it was 28VDC coil, Type N connectors, SPDT 
with the RelComm part number.  I couldn't find any data sheet during a 
web search, so I took a chance.  I was hoping that it was the failsafe 
type, where when power is removed, it switches to the NC port.  It 
turned out to be a latching type, where it stays connected to one port 
until it is switched to the other one.  Also, the 402-style relay is 
normally rated for about 1000 watts or more at 144 MHz, but this one is 
only rated for 100 watts - not enough for my 350 watt amp.

I  have found that 12VDC coil relays are more difficult to find than 28 
VDC coil models, but I have found 3 12VDC relays and 3 28VDC relays so 
far (2 are still being shipped from the Philippines and another from 
Israel).  My preamp system will be similar to this one in the top 
diagram: http://k6vhf.com/how-to-connect-a-lna-correctly/  I plan to add 
another low power DPDT RF relay (Axiom) to the input and output of the 
preamp to switch the ports to 50 ohm loads during transmit. The 
enclosure will likely be a Hammond 1590FFL from DigiKey ($23).

BTW, I also found 5 NEW (sealed in plastic) Dow Key Microwave 402-series 
Type N rated for 1.5 KW on eBay, but I wasn't fast enough and someone 
else got them for $34 each! If you look on eBay, search for Ducommun, 
Dynatech, Dow Key, Transco, Relcomm relays.

73 Roger W8IO

On 9/24/2014 8:30 PM, Dan K. wrote:
> Roger,
> Just curious but what were you expecting to get that was not satisfied 
> with this relay? I've never used a mast mounted preamp so forgive my 
> stupid question. I have been thinking about building a 2m mast mounted 
> preamp though so what will this relay not provide for that use?
> Thanks,
> Dan KF6A...
> ------------------------------------------------------------------------
> *From:* Roger Cox <rgcox2 at gmail.com>
> *To:* "MiVUS at mivus.org" <MiVUS at mivus.org>
> *Sent:* Wednesday, September 24, 2014 8:18 PM
> *Subject:* [Mich VHF UHF Society] 28 VDC Type N coax relay for sale
> In my process of purchasing relays on eBay to build a couple
> mast-mounted preamps, I bought one that wasn't what I thought it was.
> If anyone is interested in this before I put it back on eBay, I am
> offering it for $40.  Here are the details:
> RelComm model RDL-SR014
> SPDT Type N coaxial latching relay
> 28 VDC coil
> Rated DC-13 GHz
> DC-3 GHz  1.25:1 max VSWR, 0.25 dB insertion loss, 70 dB isolation
> 3-5 GHz  1.45:1 max VSWR, 0.30 dB insertion loss, 60 dB isolation
> 5-11 GHz, 1.60:1 max VSWR, 0.50 dB insertion loss, 50 dB isolation
> 11-13 GHz, 1.70:1 max VSWR, 0.65 dB insertion loss, 50 dB isolation
> RF Power (average): 100 watts to 6 GHz, 50 watts to 13 GHz
> make before break (3 ms overlap)
> switching voltage: 21 VDC
> Operating voltage: 24-32 VDC
> switching time: 20ms
> I have a data sheet from the manufacturer and photos if anyone is
> interested.  I tested S21 at work, and measured 0.03 dB at 50, 144 and
> 432 MHz, 0.1 dB at 1296 for common to the switched port. Isolation to
> the unswitched port was 100-120 dB.
> Roger W8IO
> Spring Lake, MI
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