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4m SSB/CW


#1

Do any chasers have 4m SSB/CW? My transverter is nearly ready. Invoking Theseus’ paradox in a process rather like the joke about the old broom I have built a G3XBM transverter but;

The receiver section is completely different and the transmitter section will be completely different. And, of course, the local oscillator system is completely different.

  1. The RX has a critically coupled input filter, an MMIC as an RF preamp, a TUF-25S ring mixer

  2. The oscillator uses a BFR90 feeding another (different) MMIC which feeds a magic T power splitter.

  3. The TX (still under development) will use FETS and should have an output of around 5W. It will use two 175MHz Mitsubishi RF FETS (from SDR-Kits).

I have made extensive use of SMDs to allow the complete board to measure just 8 x 10cm.

With a bit of luck I might be in a position to try it out from the shack on Sunday.

73

Richard
G3CWI


#2

In reply to G3CWI:

Go on, post a photo, you know we want to see it :slight_smile:


#3

In reply to M0TGT:

In reply to G3CWI:

Go on, post a photo, you know we want to see it :slight_smile:

He will Simon, as soon as he’s finished building the camera :wink:

73 Mickey
2E0YYY


#4

In reply to G3CWI:
Yes Richard, I do.
You might even get a few non-chasers, but 4m ops, interested in SOTA!

Unfortunately, I can’t do much tomorrow - the house is in the process of being rewired and it looks like my shack is going to be one of the last areas to be completed…

73
Graham G4FUJ


#5

Hi Hi Mickey,

Richard does seem to be a ‘do it from scratch’ kinda guy!


#6

In reply to M0TGT:

Oh dear: the penalty of working too late last night was the sight of the “magic smoke” being released from the driver transistor :frowning: Been a good while since I saw the smoke. Having had problems with the local oscillator not oscillating (fixed) I now have a PA that has aspirations to be an oscillator. Grrr.


#7

Spent the whole day fighting with the PA. Eventually I conceded defeat. I replaced the tx chain with a miniature 30dB gain 1-250MHz 1 Watt o/p SSB module that I had tucked away in a drawer (probably had it for 20 years or more). This gives 400mW o/p (investigation needed) when connected to the TX mixer. Immediate success when I was just about heard in North Manchester. Not too dreadful for a dipole slung across the shack.


#8

In reply to G3CWI:

I now have a PA that has aspirations to be an oscillator. Grrr.

Many moons back I happened on a Pye T30AM transmitter. This had a big 24V PSU, big AM modulator and a QQV6-40A for the PA. Mine was on 150+MHz. It didn’t take much effort to remove the low level crystal driver, rewind the input and output coils for 50MHz and tweak the PA PSU. I was hoping for 50W o/p with the orginal HT voltage and there were enough windings that it could be “pushed” to give about 80-90W. The 6-40A wouldn’t like that for long FM contacts but this was a 6M PA and at the time that meant SpE SSB operation.

I had the PA bias set, you could swish the PA tune about and the there was no sign of instability etc. but there was no PTT input. So I put it into operate and I applied a sniff of 6m drive and after a tune there was 40W o/p shown on the power meter. I was so pleased. I dropped the PTT on my FT690 so the drive disappeared and much to my annoyance the power meter sat steady at 40W. Drop it in and out of operate and the RF went. Apply a sniff of drive and the output came back and stayed when the drive went. Arrrggh! I had a TPTG power oscillator. Even with all the screening correctly in place I could never tame this and make just amplify without taking off.

I never did tame it :frowning:

Andy
MM0FMF


#9

In reply to G3CWI: You should start a blog, Richard. I’m sure there must be many people who have no interest in SOTA but would be interested in reading about your projects.


#10

In reply to G4ILO:

In reply to G3CWI: You should start a blog

I really shouldn’t - for so many reasons!

73

Richard
G3CWI