Latching relays

[radiogareth]

Well my 'bargain' SMA SPCO relays arrived from China eBay, https://www.ebay.co.uk/itm/113707397566 still with a usable SMA cable on one of them - the rest had been removed short with snips
A quick check on their spec shows that they are indeed 12V (@140mA) devices but that they are also LATCHING. Hmm, is this a problem or not?
Down side 3- wires to operate and some sort of control circuitry...
Upside - no supply current needed once latched - useful for portable operations perhaps.

To control them I thought about charging up a capacitor (1000uF as I had one) to 12V via suitable resistor (e.g. 1K). This operates the relay to change-over just fine. It takes about 3 seconds to charge up but of course there will be a PAIR of them, either side of a SPCO switch (or a DPCO switch which could also control DC power to the amp etc.
Not exactly suitable for QSK but for DATV or long overs possibly ideal.
Rated at 400 watts at 1.2GHz. Seems a bit hopeful if coax gets hot at those power levels.......https://www.mouser.co.uk/datasheet/2/40 ... 228654.pdf
Gareth

[g4eml]

Nothing wrong with latching relays. That are easy enough to drive. W6PQL has a circuit that works pretty well. https://www.w6pql.com/latching_relay_driver.htm

Your idea of using capacitors and a switch or relay would work but there is a chance of the relay getting ‘out of sync’ if you switch too quickly.

[G4FRE]

The datasheet says around 100W at 23cm. I have been using one at 90W for a while now on 23cm without issues and another one on the output of my Dolphin 432 Amplifier. It is also in my 10W 10GHz and 5.7GHz transverter THe feedback contacts are very useful; not enabling the PA stage until the antenna relay has operated avoiding hot switching

Luckily I had a couple of the g4hup latching relay driver boards. I provide the earth on transmit, the G4hup board does the rest

Dave
G4FRE

[radiogareth]

Plenty of options then - thanks for the links. Based on the 'sluggish' problem I thought of passing a pulse via a capacitor to a driver device. Then found that is exactly what W6PQL did.....he seems to have gone OTT on the driver spec though, 8 amps at 100V. IRF501 and a diode would do that. Especially as I have those....
Onward....
Gareth

[g4eml]

I agree, with modern devices the circuit can be simplified quite a bit. The basic idea remains the same though.