SSTRAN AMT3000 peaking

[petervk2mlg]

I have just completed one of these kits. While I have it working, I'm wondering about following the peaking instructions.
In the instructions it suggests having your voltmeter set to read about 15 volts.
When peaking mine I only get a maximum of about 4.5 volts DC. I'm using a modern style DMM.

Peter

It's the peak that matters, 15V was recommended as a start and is good enough to detect the peak. Super 'modulators' these.

[ukcol]

Hi Peter

Your aerial will have an effect of course. If your "peak" occurs when the trimmer is fully meshed or fully unmeshed then the true peak may be out of range of the trimmer suggesting something is wrong. If not it is probably fine. The voltage from your AC adaptor will have to be up to spec too.

I built one of these 3 years ago and have been running it continuously since, As MM says an excellent bit of kit.

I can't now, but if you still have a problem after 12th August, I can take the lid off mine and make a measurement for you.

I could be wrong (memory isn't my specialist subject) but I don't think mine produced anything like 15 volts. Mine is tuned to the LF end of the MW band which may also be a factor.

[petervk2mlg]

Thanks Colin,
That's be good when you get a chance. My transmitter is working, but I'm curious as to what voltage to expect. My transmitter is tuned to about 801KHz. I'm just using the length of wire supplied with the kit as an aerial.
I know Igranic added a tuning meter to his unit, but I don't think he posts any more.
Peter

All short aerial (oops, loading capacitor) modulators work best at a higher frequency. For a guess, twice the frequency, four times the effective output (TX and RX antenna efficiency add/multiply up). Mine is set to 1350kHz and leaks quite well. Mind you when there is a nice gap in LW I may make a helical 'loading capacitor'

[petervk2mlg]

Here is Phil Bolyn's (SSTRAN) answer to my question re peaking.

4.2 VDC is correct for operation at the high end of the band. This is just an uncelebrated, relative indication of the signal on the antenna, sort of like a built in relative field strength meter. The purpose of the meter circuit is to give you a visual indication of tuning and make it easier to set the tuning to the peak.

The fairly high value (220k) resistor R14 in series with the diodes D5 and D6 in the meter circuit provides a very reduced sampling of the voltage at the antenna. The small sample is just enough to produce a few volts for the meter, and is small enough so as not to adversely affect the output signal.

Phil Bolyn
SSTRAN

[ukcol]

Hi Peter

It looks like you received the info you needed while I was away, but here is my measurement as promised.

My AMT3000 is tuned to 567kHz and peaks at 7.0 volts.

[petervk2mlg]

Hi Col
Many thanks for taking the time and trouble to measure that peak.

Peter