Coax Relays 1296

[VK3WE]

Hi all,

I need to source two coax relays for the 23cm band? Can someone recommend a brand and model? Also a supplier?

thanks for your advice,

de
Rhett VK3VHF

[VK2OMD]

I need to source two coax relays for the 23cm band? Can someone recommend a brand and model? Also a supplier?

You haven't given much detail on your application.

You will see relays go on VKHAM from time to time, I have bought new coax relays for upwards of $40. You will see relays on Ebay, but they probably come from the US. Don't forget the availability of the US Post $11 flat rate envelope, it is an economical way to get a couple of relays posted.

A couple of us recently bought some Dowkey pulse latching relays (new from the Dowkey distributor) for about $150 ea, excellent specs, no holding current, but you can't drive them directly from a PTT line. I designed a generic coax relay driver for adapting the relays to PTT control and they work fine (http://www.vk1od.net/crd/index.htm). The driver supports two fully independent relays (which could be of different type).

A certain seller in Melbourne may be a source of relays, he often has inexpensive SMA relays... but you didn't mention your power level etc.

Otherwise, Google for info and expect to pay anything up to $600 + shipping depending on your requirements.

Owen

[VK3WE]

Thanks Owen,

I'm currently using Tohtsu CX-520d relays for 2 and 70, but for 23cm I suspect these relays maybe at the upper limits of there specifications. I'm seeking advice on what others are using for the 23cm band?

Thanks for your website info Owen, I'll check it out

Rhett VK3VHF

[VK2OMD]

Rhett,

A couple of thoughts:

You need to consider your power level. If you look at most relay ratings, their power ratings are the power that would result in about 2W of dissipation in the relay given the published loss figures at the frequency of interest. If you plans are to use QRO, then your approach will be different to using say 100W. Don't forget that relays should be cold switched, and that the average power of SSB telephony is real low (~3% of PEP), so you can easily handle high power SSB telephony in most relays, but they may wilt under JT65x.

Relay loss will also roll up into your system G/T (see http://www.vk1od.net/gt/index.htm for discussion of G/T).

Required isolation will depend on your power levels (including that from adjacent antennas) and preamp tolerance.

Owen

[VK2KRR]

Hi Rhett

I chose the Tohtsu CZX-3500 for my 1296 station. They are in the shack and the amp runs 120W directly into one with no problem on JT65.

You can source them from somewhere in Melbourne, David VK3HZ advised me of the business, there were very good and got them to me in a few days.

It could have been this one I think http://www.imark.com.au

[VK2OMD]

Hi Rhett

I chose the Tohtsu CZX-3500 for my 1296 station. They are in the shack and the amp runs 120W directly into one with no problem on JT65.

Tohtsu specs are an interesting read.

For example, looking at the CX-600NL, it is rated at 1GHz at 1kW, and 0.15dB insertion loss. The insertion loss implies a loss of 34W of loss for 1kW input. I seriously doubt that the specified loss and power rating are consistent. My suspicion is that the CX-600NL probably does have 0.15dB insertion loss at 1GHz, and is probably good for somewhere from 60 to 150W continuous power.

Be critical of coax relay specs. In the absence of reliable data, measure the insertion loss and figure the maximum continuous power to be the quantity that would dissipate 2W to 5W in the relay.

Owen

[VK2XSO]

Depending on the changeover time required and the application, a single baseball coaxial switch should be able to do the task of one or two relays.
They're often rated to 15GHz with a reasonable amount of power. I seldom see them used by hams, but you can occasionally find them on ebay for a reasonable price. I have them for SMA, BNC and N and often recover them from old surplus gear.

There were several microwave converters at the NSW WIA Trash n Treasure. They sat around for a while until a few hams realised that they contained such gems as YIG's and baseball switches. I think I saw a few still on the shelf last TnT.
Might be a bit of a drive from VK3 for what is usually a very lame event. I'd guess a few of these converters might turn up at Wyong field day this year. Could always tray asking for them on vkham.