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GM Jim,

At 14/10/2018, you wrote:

Raj,
I thought the same thing, but maybe, even using sockets, just for the experiment, I could get some relative comparisons between the types to see if any were better than others. I suspect the 500mw version, Arrow part# V23105A5503A201 will be the best because they have the lowest coil resistance, fewest turns on the coil. The only thing that worries me using that relay is it's current draw - I'm hoping it won't be too much for the switching transistors in the uBITX. The 400mW relays are working and switching OK but the additional current from the lower coil resistance may become a problem and I'm not sure yet.

400mW is 33mA that should be OK for the transistors. I will try lower current one when I find a cheaper source or a vendor who will send
me by USPS.

I don't want to risk ruining the board by soldering and unsoldering the relays several times so planned on using sockets but ONLY on the one board I'm planning on setting up as a test station. I'll build it up on a board but use double shielded Teflon insulated COAX from the uBITX boards 2 pin connector to the BNC output and make all digital and audio wires twisted pair to the front panel jacks, encoder and switch. The construction will be open, no case but the uBITX board will be mounted on a 16 gauge aluminum plate to give a good underside ground plane and good low Z grounds for all connections.

Thats sensible, I put in sockets for the same reason. That board with L5/7 changed had spurs below -50dbm and its put to rest.
I was thrilled with Mike Doty's find (Remember Roy Doty ? - PopSci). I ordered the same 400mW relays as I thought that lower
power ones MAY be a little different in construction. Just KT1,2,3 change should do the trick. The other two don't play much
of a part in harmonics leaking through.

I tried a lot of mods, most gave a few dbs of improvement while others made things worse. The fix that makes dramatic improvement is
the root of the problem. For spurs the TX signal leaking into the first mixer was cured with TX losses with a 45MHz filter.. further thinking
led me to L5 and its position made a difference but not a fix.. the SMD for L5 made a big difference. Sort of a eureka moment!

High Q inductor in this board layout is not in best interest of impedance matching.. we are only stepping up 50 to 650 Ohms and back.
I need to experiment with a tapped toroid 2:7 without the caps and see - that might also fix the spurs issue. I wish someone would try
that and report - I am at my farm.

I have some good, gold plated machined pin socket strips that are very low profile and will use those to create the sockets. Again, for these tests I will only look for which of the 4 relay types gives the best harmonic attenuation between types and then I will solder that set into a uBITX for the final results. Only way I know to test all 4 types without possibly ruining a good board from too much soldering/de-soldering of relays. A repaired trace would negate the original test results as it's characteristics would be different.

Hope people can understand what I'm trying to say here.

I read you! I added the same pins. With a collaboration like this group we will make a great and simple exciter / QRP rig!

Jim

Raj

------ Original Message ------
From: "Raj vu2zap" <rajendrakumargg@...>
To: [email protected]
Sent: 10/14/2018 1:06:47 AM
Subject: Re: [BITX20] Harmonics and Relay Replacement

Jim,

My take on this relay business is that both contacts are being inductively coupled.

Imagine the NC contacts on one side - it is a loop and will be inductive. The same goes
for the other pair on the other side..

By adding a socket we may not get the best rejection from Axicom relays. I have also
socketed KT1/2/3 .. the relays have arrived and I am at the farm.. so a week more
of suspense.

If someone with a SA like 815 can feed in the tracking gen through a 47 ohm resistor
to one NC contacts in/out and take the Analyser input from the other NC contact set
and then sweep say up to 100MHz, we get some enlightenment. I am eagerly waiting
to try for myself.

Raj

At 13/10/2018, you wrote:

Looking at the differences between the original Hongfa relays -S (for sensitive) version in my uBITX boards and the Axicom relays Mike Doty and I installed in place of them, the Axicom had lower coil resistance in the 400 mW coils vs the 200 mW coils fot the Hongfa relays. That means fewer turns of wire in the Axicoms and subsequently less inductance. That may be a huge factor in the isolation between the two types. The coil resistance for the Axicom that matches the Hongfa in DC spec aldo has the exact same listed coil resistance.

I'm going to order 5 each of the 150mW, 200 mW and 500 mW versions, put sockets on my 3rd V4 board and see how much difference there is between the 3 other types relative to the already installed 400 mw version. Hopefully that will give us some definitive answers. Be Monday before I can order them so it will be a few days before any testing can be done.

Jim Sheldon, W0EB