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OK, All I did was change the configuration of L1 by rotating it 70 degrees CCW and now I have stability. Hard to believe that small change made such a huge difference. The power output at 12V is around 650mA. Transistor runs very warm, and the RF frequency is now registered on my counter like...
"But as a "measurement instrument", bridge is fine (and broad band) to measure antenna input impedance. "
So If I was to make that bridge, I would connect it to my transmitter and antenna and it would let me know if the antenna is a good match for the transmitter by the LED not lighting up?
OK, I got my hands on a new 2sc1971......tried it in the circuit, and it worked, but could not get it to tune properly. I switched the circuit to the one below. The circuit draws around 850ma at 12.5-13v, and puts out major RF on my field strength meter. The transistor does not get very hot...
Thanks for the reply. It just goes to show that people place bad /non-working schematics on the internet.....why they would waste their time I will never understand. I have everything for the schematic you told me to look at. The 10pf trimmer is used for fine tuning? Anything else you can tell...
I am only looking for a simple circuit that will let me know if my antenna is matched fairly close. NOT looking for total perfection. Any idea what the proper way to use/adjust it is?
Thanks.
I just added 8pF to the input side of the meter where the 10pF is mounted. I am now able to set the meter. Should I add the same amount to the other 10pF cap? I left everything else untouched.
Thanks
I'm trying it right now. I have a 1W Fm transmitter set at 93mhz and connected to the swr meter with a very short piece of coax. I have a dummy load connected to the swr meters ANT output. When I go to set the meter(Place switch in the "Set" position, then power up the transmitter, and adjust...
I have no intention of even using it above 250mhz. I hardly paid anything for it, so modification is worthwhile to me. I'm going to open the unit and post a pic of the inside of the unit(Biff44).
Thanks!
I have one of these laying around:
Workman 104 VHF/UHF SWR/Watt Meter
It was designed for 120mhz - 500mhz. I'd like to lower the frequency range to 80 - 450mhz. The SWR portion does not work under the 120mhz bottom of the range. I cannot set the meter.
Any ideas how? Thanks.
How about swapping out the transistor with a 2n3866. That should let me know if the 2sc1971 is fake since it tests as good.
---------- Post added at 19:37 ---------- Previous post was at 18:37 ----------
OK. I soldered in a 2n3866. I'm now able to draw current/and adjust everything. Must be a...
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