Equipment

Testing the Siglent SVA1015X

Been playing a bit with the SVA1015X today.
Here are some snap shots.

Noise floor @ 10MHz, preamp off

 

Noise floor @ 10MHz, preamp on

 

Measuring Rohde & Schwarz SMT02 Phase Noise @ 15MHz

 

Measuring my 10MHz GPS disciplined oscillator Phase Noise.

 

Measuring SAV1015X internal osc Phase Noise.

 

Next pixs; testing one of theese, terminated into a 51 Ohm resistor with the VNA function.

 

Banana to BNC adapter. VSWR: 10MHz to 1.5GHz

 

Banana to BNC adapter.
Smith chart: 10MHz to 1.5GHz

Santa, ehhh sorry, the postman just brought in a new toy here.
It is a radio, but not HAM-radio, sorry.
It is time to retire my soon to be 30-year-old Sony FM stereo receiver.
The successor is going to be this Yamaha Network/FM/DAB+ receiver, which has all kind of bells and whistles. (Just barely tested it, but it sounds very good)

Yamaha R-N803D Network Receiver

After serving me for many years, my good old keyer, microham mkII stopped keying last night.
Of course this happens at the least convenient time, during a contest.
I got an idea of where the fault lies, but if any of you guys has a schematic if the MKII lying around, I would VY much like a copy.
73 de LA6TPA
Geir

Failed Microham MKII

Here is a Saturday morning update report regarding my rf switch project.
Back to the good old drawing board, I guess.
Switch are switching ok, and loses are acceptable, this is fine.
However, it is picking up ambient noise. I suspect its being a shielding problem and an isolation problem between RF parts and DC parts of the relays.
To give you an idea of the rx degradation with this thing is in line compared to the narda 023.
Pointing the 144 array to a relatively cold spot, the wsjt noise floor rises about 4dB, and this is simply not acceptable. This thing is useless for weak signal work until these problems are rectified.
I have now installed a narda 023 again.
Hoping to do some EME contacts again this weekend. See you on the moon.

Morning report: Saturday 25.03.2017, still messing around with my quest for low cost high power rf-switch. I have cut and soldered a lot-lot-lot-lot-lot of coaxes since last post and….. Well, now it is looking really good, I have exchanged all the small diameter coaxes with larger ones, and there are now no heat loss I can feel with my fingers!
Operator is a bit too eager going on with the testing here, not checking all connection beforehand, resulting in the SSPA safety system trigging several times before it get going. (shame on me)
Here are a some pix & unabridged videos:

Been quite busy experimenting with this rf-switch the last couple of days.

There has arrived a lot on and off-list comments regarding rf-switches and I have not had the time to answer all, but thanks.

I am now up in what I call revision 4 switch.

What’s new:
Revised schematics for better RX/bypass-port isolation.
New 10 amps relays.
Have done a lot of λ/4 coax tuning.
TX loss is slightly better.
RX loss is slightly worse.
RX isolation is much better.

What needs to be done:
Switch works but the 75 ohm rg-179 stubs are getting way to hot when passing the Kw level.
Need to find something better.

Revised schematics for better RX/bypass-port isolation.

I have got some questions about the home brew rf-switch or relay in my previous post.
To clarify, I got this idea from Leif, sm5bsz web site.
He has done this with PIN-diodes. I don’t have suitable diodes on stock here so I substituted those with small relays. Problem is that lo-Z current at the relays are way to large, and I got to do something with that. Upgrading to larger relays would only make the Q higher and move the problem over to the coax subs I guess. I think. What is needed, is to lower the Q, maybe by adding a small resistor at the relays, say for example 0.1 ohm. (at the point of writing this, I must emphasize, I have not done the math yet.) But I have a feeling it my work. We will see………  🙂 

UPDATE: I have now done the math, and installing a series resistor at the lo-Z point will not lower the rf-current. It will only increase insertion loss. RF-current is about 4,2 amps, and my small signal relays are rated 2 amps @ 30VDC, Guess I got to find some larger ones.

Simplified schematic

This is a drawing of the voltage & current sensing board. If you look further down on my site, this is the board on top of the rf-deck with red wires going through blue hall-effects elements. There is some more stuff on this board, and this is the VDD FET switches, but these are not in detail in the drawing.