[NLRS] 10 GHz relay

Tue Aug 12 18:11:06 EDT 2014

I've been using a Dow-Key transfer relay on my 10G station since I 
assembled it. Its showing intermittent 10% or more insertion loss on 
transmit. My Transco catalog shows the type HO 700C family transfer 
relay with SMA as having 60 dB minimum isolation from 2 to 18 GHz with 
typical about 82 dB, a little less than the 919C family which shows 65 
dB min and 89 dB typical. Either one is good enough for our power levels 
and the levels that the relays will stand. The 700 series transfer relay 
will handle 50 watts at 10 G and 239 watts at 400 MHz with SMA 
connectors. So the contacts are more substantial than the 919 family 
with a slight cost in isolation probably the contact size is less 
important by the transfer relay being built with a greater open contact 
spacing and the possibility of terminating the unused port.

In my station I put a 50 ohm termination on the fourth port so either 
the receiver or the unkeyed but powered PA sees that when not in use, 
though during the time of relay changing position all ports are open. 
Sequencing is important and I have changed mine to give the relay a 
better chance at survival. I need to change it even more. I might during 
the winter. In the mean time its manual PTT for SSB and CW, no VOX or 
KOX and no FM.

A ground or termination on the fourth port should increase the in 
circuit isolation over leaving that open or using a SPDT relay that 
leaves the receive port open on transmit. And when the relay contacts 
are a significant fraction of a wavelength apart there can be lots of 
odd phenomena to decrease isolation and increase insertion loss.

I think that Transco will survive so long as you don't key RF with it. 
Switch it only cold, that's what sequencers are for.

73, Jerry, K0CQ

On 8/12/2014 3:52 PM, Arliss wrote:
>
>
> Thanks, Jerry (and Donn, from a direct email). I now feel better about
> using the relays I have on hand.
>
> Digging around in my junk, I found some Teledyne Microwave transfer
> switches. It's my understanding their isolation is less than the SPDT
> types because there are 2 leakage paths rather than 1 (?). On the other
> hand, they would allow the receive port of the transverter to be
> grounded on transmit (I think that's correct).
>
> I think I'll just go with the Transco.
>
> Thanks again.
>
> 73, Arliss
>
>
> On 8/12/2014 3:53 PM, Dr. Gerald N. Johnson wrote:
>>
>>
>>
>>
>> On 8/12/2014 2:11 PM, Arliss wrote:
>>>
>>>
>>> Hi,
>>>
>>> I'm looking for information on what relay I can use to switch
>>> the output
>>> of my 10 GHz amp. We're talking 8 watts out. I have a Transco
>>> 82152-919C74700 and a MaCom MA7530-S134 -- both with SMA
>>> connectors.
>>> Perhaps I just missed it, but Googling the part numbers gave me
>>> some
>>> hits, but not information such as power handling ability and
>>> isolation.
>>> I'm wondering if anyone out there can offer some guidance.
>>
>> One of my Transco catalogs says the 919 series SMA is rated at 14
>> watts at 10. 20 watts at 4 G, 39 watts at 1 G, and 59 watts at
>> 400 MHz. That's switching cold, not hot.
>>
>> Transco numbers are now sold by the Dow-Key division of Ducommun
>> and listed in those catalogs on line. The power ratings for
>> Transco relays is in a chart on page 6 of this catalog, power
>> rating isn't listed on the pages for the part. The part page
>> shows 65 dB the minimum specification for isolation at 10 GHz
>> with typical isolation about 89 dB.
>>>
>>> Also, I have an HP coaxial switch: 8765B OPT 015 100, rated
>>> from DC-20
>>> GHz. It says maximum power is 2W, which I assume is at 20 GHz. The
>>> rating at 12 GHz is probably higher, but I'm guessing
>>> substantially less
>>> than 8 watts. Does anyone know better?
>>
>> I found an HP applications note that says 2 watts is the absolute
>> maximum at DC because the contacts are very tiny to work at 20
>> GHz and can't dissipate the heat from any higher power. They were
>> made for instrumentation, not transmitting.
>> www.keysight.com/en/pd-1000002314%3Aepsg%3Apro-pn-8765B/coaxial-switch-dc-to-20-ghz-spdt?cc=US&lc=eng
>>
>>
>> offers the latest datasheet and applications notes. Keysight is
>> the new
>> name for Aligent electronics that went into use August 1st. Spun off
>> again.
>>
>> I'm finding some apparently new relays at 3 watts are showing a
>> 10% power loss even when rated to 26.5 GHz when tested at 10 GHz.
>>
>> I don't find anything on the MACOM or the DynaTech relay on this
>> computer. WA1ZMS works for MACOM, he might have inside information.
>>
>> If switched without RF the Transco should do OK if its not got a
>> stray 10 GHz resonance to cause excessive insertion loss. I have
>> a Transco transfer relay that measures good and just received a
>> new 919C70100 that I've not tested yet. Need to get one of them
>> on the 10 GHz rig very soon. I have a Dow-Key transfer relay that
>> shows that insertion loss sometimes. Its gone intermittent. I
>> have a Ducommun rated to 26.5 GHz that shows that loss all the
>> time, its magnetically latched.
>>>
>>> Thanks & 73,
>>>
>>> Arliss W7XU
>>
>>> 73, Jery, K0CQ
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