Lash up Direct Conversion Receiver

[pwdrive]

Just had a good scour round and found an old gold bonded switching diode (OA5) thought I must fiddle around with this....Connected it from grid of the harmonic gen to deck (cathode to deck) while feeding the signal to the grid from the donor 1 Mhz osc, the result was that the mixer conversion gain has noticably increased on the higher harmonics, I thought it might have a chance but was supprised that it did....So there yer go.

Lawrence.

[pwdrive]

I did a couple more tests on the regenerodyne this afternoon, up till now using the harmonic generator I have been mainly using Fo above Fs, this afternoon I put it through its paces using Fo below Fs, it works a lot better as the harmonic output available to the mixer is larger using the lower harmonics.
The other test I did concerns frequency stability, I have no frequency counter so I used the zero beat method.
The regenerodyne and the B40 (the donor osc) were switched on and allowed to warm up for 1 hour I then did the test at 10 Mhz by tuning in to the WWV standard, the signal was tuned in and the regen detector was brought into oscillation, the signal was then tuned for an exact zero beat, I then left it, coming back 1 hour later I could not detect any audiable beat drift, that is not to say that there is'nt any drift at all but it does say that audiably there wasn't any all I was getting was the thud thud as the WWV signal was ticking away which is what I had when setting the initial zero beat.
So, conclusion...The 1 mhz osc in the B40 is solid as a rock, the regen detector when brought into oscillation also seems to be solid.
Need to bear in mind that the regen det was oscillating at the low end of its range (2 Mhz) and not the high end (3 Mhz) as I am now using the harmonics below the signal frequency to select the Mhz band.
I have not got any 80 meter coils or any for bands below 80 meters (ie: 160) wound at the moment but when I do I will go back to using Fo above Fs, obviously....Having said that the harmonic generator tank can be tuned to the fundamental for Fo below Fs coverage of the 80 meter band.

Lawrence.

[pwdrive]

Hear is the test I did, not under ideal conditions as I am limited to what test gear I have.
The aim of the test was to try and get a better idea of unwanted harmonics rejection.
Test frequency is 10.1 Mhz.
Harmonic selected (from the 1 Mhz fundamental) is the 8th (8 Mhz)
Regen det tuned to 2.1 Mhz.
RF amp tuned to 10.1 Mhz.
Harmonic Gen. tank tuned to 8 Mhz.
Regen control set to just past the point of oscillation.
RF gain set to max.
Sig gen was connected across the antenna input, modulation off, antenna disconected
Output measurement consists of an Avo 8 set to the 10 ma AC range and connected directly across the speaker.
With the volume set to a tolerable level the sig gen was tuned to 10.1 Mhz to get a beat, the beat was adjusted to approx 400 cps the sig gen output was adjusted to give a 1 ma reading on the Avo, the results are given below the sig gen input voltage to it's attenuator was kept constant at all frequencies, note that the maximum output from this sig gen via its attenuator is 25 mv. All control settings on the regenerodyne remained at their initial settings.

8th harmonic:
Plus = 10 uv @ 10.1 Mhz for 1 ma o/p
Minus = 15 mv @ 5.9 Mhz " "
9th harmonic:
Plus = 6 mv @ 11.1 Mhz " "
Minus = more than 25 mv @ 6.9 Mhz " "
10th harmonic:
Plus = 25 mv @ 12.1 Mhz " "
Minus = more than 25 mv @ 7.9 Mhz " "

7th harmonic:
Plus = 13 mv @ 9.1 Mhz " "
Minus = 22 mv @ 4.9 Mhz " "
6th harmonic:
Plus = more than 25 mv @ 8.1 Mhz " "
Minus = 20 mv @ 3.9 Mhz " "
5th harmonic:
Plus = more than 25 mv @ 7.1 Mhz " "
Minus = 13 mv @ 2.9 Mhz " "

Lawrence.

[Yorkie]

You're certainly having fun with this project Lawrence - thanks for sharing your findings with us. One of the appealing aspects of homebrewing is that the enjoyment derived and knowledge gained bears little correlation with money expended. Indeed, some may argue that enjoyment is inversely proportionate to expenditure! As the G-QRP Club's motto, (based on 'Occam's Razor') says: 'Tis vain to do with more, what can be done with less'.

[pwdrive]

You're certainly having fun with this project Lawrence - thanks for sharing your findings with us. One of the appealing aspects of homebrewing is that the enjoyment derived and knowledge gained bears little correlation with money expended. Indeed, some may argue that enjoyment is inversely proportionate to expenditure! As the G-QRP Club's motto, (based on 'Occam's Razor') says: 'Tis vain to do with more, what can be done with less'.

Yes David, I am certainly learning a lot.....Or may be remembering a lot since starting this project, trying to remember various + & - products from various harmonic frequency mixing processes certainly taxes the brain. I think I will have an early Xmas and get myself a 'scope and a frequency counter or may be just draw a straight frequency domain line on a piece of A4 and mark off the harmonics.

Glug Glug Glug....This damn weather...

Lawrence.

[pwdrive]

For want of something better to do this morning I lashed up a basic VFO (6J5 tuned grid) to try out, works very well but obviously there is some warm up drift also tuning the RF pulls the VFO, not to far but far enough to be quite noticable on SSB so I removed the injection coupling capacitor and replaced it with a small value trimmer and adjusted the injection for best mixer gain coupled with minimum pull, to that end it is quite good now up to 18 Mhz. I also put the tunable IF range back to 500Khz as the regen det. works better with it like that, probably because the cathode tap is now at 3 turns rather than 4 turns as was required when using a tunable IF range of 1 Mhz.

Lawrence.

[Skywave]

Lawrence: haven't heard much for you lately about this project: what's the latest news, please?

Al. / Sept. 07, 2012 //

[pwdrive]

Lawrence: haven't heard much for you lately about this project: what's the latest news, please?

Al. / Sept. 07, 2012 //

Wel.....It's like this.....I'm on concrete duty, big time.... Yesterday and today I have mixed and laid approx 5 tons of stuff, I have about another 6 tons to do but have run out of three quarter to dust until Monday, we can only get a 7 ton gross lorry up the track, the waggon carries about 4 1/2 tons max so will need another delivery after the one on Monday, I am doing the floor in the new log shed/car garage plus a concrete raft for my Landrover garage to be and also the footings and floor for our proposed extension which will be the radio room! The Regenerodyne still lives, I have not fired it up for about three weeks as I have an R1155 on the bench at the moment and pondering wether or not to do a refurb or leave it 'till I have less house DIY to do, I am tempted to leave the R1155 until I have more time as I don't want to rush the refurb.
The Regenerodyne as last developed is now running a lashup on chassis VFO, this works fine, the plan is to use that and also have it switchable as a straight amp for an RF Sig Gen input. I have not done anything since on the harmonic generator idea though I am not discounting the idea completely, neither have I as regard to using switched Xtals for the dedicated amature bands. As you know the HG idea does work but the mixer drive output is low compared to a purpose built VFO, I thought the VFO I rigged up might drift to much but it seems fine as far as valve VFO's go, I checked it at 10 Mhz on WWV and it was no worse than say a Hallicrafters, HRO etc, obviousely it needs refining it's a tuned anode job with grid feedback winding. When the time comes I might have a go with a Colpitts, that will reduce the VFO tuning per range but for amature SSB reception it does not really matter as the band ranges are fairly narrow anyway.
Whichever way, with various combinations of osc/mixer drive I still intend for it to cover from the bottom end of Top Band up to and including 10 meters. Probably go for homebrew plug in coils a la HRO, Eddy 358x etc, audio output will be included but PSU and speaker will be seperate for stability reasons (heat/vibration etc)
So there we go....What's your latest project Al?

Lawrence.

[Skywave]

Thanks for your reply, Lawrence.

Things here? Not that dissimilar to your activities: outside stuff. As you know, this year has been extraordinarily wet, so a lot of 'outdoor things' didn't get done. But now that the weather has cheered up, there's a backlog of work to attend to - mainly house and garden maintenance.
One unexpected and unplanned item in my list involved my general purpose 'long-wire' aerial. At the rear of the house I have a pole secured to the back wall, the top of which secures one end on that aerial. Now when I put that pole up (many moons ago) I was short of suitable material for such a pole. What I did have was a length of steel pipe, about 1½ in. diameter and another length of a wooden pole about same diameter. I simply joined the two together with a 12" length of copper tube to make one mast: the wooden section was at the lower end and was suitably treated to withstand the weather. A few days ago, whilst sitting in the garden with a cuppa, taking a break from some painting, I noticed that the bottom 6 inches of that wooden pole was sticking out at about 30 degrees: it had rotted through where the U-clamp was securing it. Fortunately, about one year ago, I 'acquired' a 12 foot aluminium pole from our local ambulance station. They had just completed an aerial refit. I had been looking at this discarded pole lying on the ground by the side of their building for weeks as I passed by and thinking "Hmm". I eventually plucked up the nerve to ask. "Help yourself, mate!" came the reply. So I promptly said "thank you" and scarpered with it, el pronto, before he changed his mind! And now I'm glad I did - a perfect and improved replacement mast - and a good deal lighter too.
I must get around to taking a few photos of it and sending them in - after all, a picture says a thousand words.

Ah! A 'few words' have just been voiced from the kitchen!
O.K., tea-break over: back to work.

Al.

[Skywave]

Re: my previous post above: my aerial arrangements at the 'house end':

[attachment=5831]

There is the occasional requirement to do TV maintenance: hence the TV aerial, which feeds the workshop only. The 'spiky aerial' is a broadband vertical omni., (alleged 50 → 1300 MHz) that feeds an Icom R7000 scanning receiver: 25 → 1 GHz coverage.

Al. / Sept. 24 2012 //