SWR meter - Do it yourself project

[guy1a]

Any idea what i am not doing correct ?

No matter what side i connect. I get 0.0 volts.

The tx works since i can see the video on the display.

[NDw]

What power is the tx? With my 10mw tx's I get no reading at all.

[NDw]

Do you coil and protect from the RF the detector voltage wires that go to your voltmeter?

I've made up a shielded connector. But what side would I connect the shield to ground on, the detector side or voltmeter side?

I also tried just connecting the voltmeter to a battery and turning the tx on right beside it to see if it effected the voltage measurment. And even in 500mw mode it only changed it by about 0.1 volts.

[NDw]

You may check the antenna if there is a connection between BNC center pin and the whip, also for short between center pin and ground.

Thanks. There is no short between the centre pin and ground. Ands to check if the whip is connected to the centre pin I'd have to cut apart the antenna. But the readings on all my antennas seem surprisingly bad.

[guy1a]

What power is the tx? With my 10mw tx's I get no reading at all.

It is 20 mw

You think it is too slow ?

[NDw]

I think so. But IB or Mictronics would need to confirm.

[jalves]

@NDW,

I would say connect the shield only in ONE side, and I bet connecting it to the detector ground is better.

I use a twisted servo wire coiled with 4 to 5 turns, no problems with induced voltage due to RF in it's proximity.

@Mic
When you said "200mW should give you 2-2.5V forward", this happen with a good antenna (low SWR), right?

I ask because my detector gives 2.3V with 500mW DL with its regular whip. Could this somehow low voltage be due to the hopping scheme used in the DL?

[NDw]

@NDW,

I would say connect the shield only in ONE side, and I bet connecting it to the detector ground is better.

I use a twisted servo wire coiled with 4 to 5 turns, no problems with induced voltage due to RF in it's proximity.

@Mic
When you said "200mW should give you 2-2.5V forward", this happen with a good antenna (low SWR), right?

I ask because my detector gives 2.3V with 500mW DL with its regular whip. Could this somehow low voltage be due to the hopping scheme used in the DL?

What kind of reflected voltage are you getting?

I've just tried running the power wires through my lc filter, which has about 25 turns of + and - and still basically the same readings.

[jalves]

What kind of reflected voltage are you getting?

Vreflected=0.98V --> articulated whip SWR calculated=2.5

[Mictronics]

It is 20 mw

You think it is too slow ?

That's to low. You need enough input power to overcome the breakthrough voltage of the diode. Not sure yet how much is needed but I think 100mW might be required.