New England AM QRP Net - Need NCS For This Sunday

[W1UJR]

Hi fellows, will be out of town for biz again this weekend, last weekend Raleigh, this one Dallas, and need some one to fill one for me as Net Control Station for the New England AM QRP Net.

We've got a good thing going, and I'd like to see it keep rolling along.

It's pretty simple, just call up the net at 3PM Sunday afternoon on 3.880, take down the calls of stations checking in, and encourage folks to talk about themselves and their station.

Let me know here or via email if you have questions.

Thanks!

-Bruce

[W1RKW]

I'd volunteer this Sunday but my schedule is up in the air. If it's conducive I'll be there to handle things otherwise, someone else needs to step up or be backup.

[WU2D]

Frank,

The conditions were not so hot on Sunday. Nice group at 3PM but you guys need to move down away from the window a little more. I was having problems hearing not because of the power level, but because of the QRM. Now I have to admit that I was using my TCS twins and that receiver is wide. But the 7 Watts I was producing was also giving neighbor AL VTP a hard time so I know we were close.

I am working on moving my Widowmaker 50C5 up to 75M for next Sunday. that rig is a 12BA6 ECO into a 50C5 modulated by another 50C5 and a 12AX7 mic amp. The modulation method is 100% Heising. The Widowmaker uses an off the line voltage doubler power supply and it is built on a board. She does about 1.5 Watts and I hope to get this up a couple of dB. I would think it should do 2-3 W out with 350V on the plate.

Mike WU2D     

[WU2D]

OK I got the beast up to 5 Watts out with good audio, fairly high modulation and not too much hum. The trick was changing out the RF Choke on the ECO plate to a tuned circuit to get more drive and reducing the Heising series network resistance from 5K to 2.2K. You mat remember that a trick to get 100% modulation with simple Heising is to put a resistor from the reactor to the plate of the RF tube and bypass it with a capacitor.

The primitive Hartley ECO PTO is a bit squirrelly and I will work on that. The L was optimized for 160M. I need to take some turns off and up the C and change the tap.

Ready to Strap Sunday. Might need a critical test this week with W1VTP Al.

Mike

[w1vtp]

OK I got the beast up to 5 Watts out with good audio, fairly high modulation and not too much hum. The trick was changing out the RF Choke on the ECO plate to a tuned circuit to get more drive and reducing the Heising series network resistance from 5K to 2.2K. You mat remember that a trick to get 100% modulation with simple Heising is to put a resistor from the reactor to the plate of the RF tube and bypass it with a capacitor.

The primitive Hartley ECO PTO is a bit squirrelly and I will work on that. The L was optimized for 160M. I need to take some turns off and up the C and change the tap.

Ready to Strap Sunday. Might need a critical test this week with W1VTP Al.

Mike

Just give me a message here Mike

[WU2D]

Al I have a day off on Friday so we can give it a try in the PM - Mike

[w1vtp]

Al I have a day off on Friday so we can give it a try in the PM - Mike

Sounds like a plan.  I get home a little after 7 PM. 

Al

[WU2D]

The maiden voyage after converting the Widowmaker from 160M to 75M was today.

I was heard by W1UJR Bruce in Maine and WB2LOI Harvey near Albany, so 4 Watts is fine at 3:30 PM on Saturday Hi. The audio is muffled so I have to find out what that is all about. It is not a great looking modulation envelope on the scope - no highs and not much upward modulation. Back to the bench! This is an old schematic with a few errors - the 12BA7 is a 12BA6!

Mike WU2D

[Ed/KB1HYS]

Dang, I heard they guys working the net along with some AWA (?) stuff.  I was working feverishly to complete my QRP AM rig...  

Now Get this:

A TPTG (Tuned Plate, Tuned Grid) Self excited oscillator, using a 6N7 with both sections paralleled. The tube is plugged into an octal relay socket, that way I can repower with any octal tube I want and experiment to my hearts content.  It's ppwer supply is from an old TV power supply, with added choke input filter sections for hum reduction and regulation. Works pissa, a little bit of chirp on the CW signal, but not bad at all.

Modulator by a modified Heising hookup using an unknown DC Filter choke, and 0.4uf worth of 600V caps, with an 8-ohm to 1k ohm output transformer acting as the mod tranny.  Fed by an old guitar amp using a microphone from an old telephone handset.  lots of clip leads and loose wires running around...

The trace on the scope looks ok. Audio sounds like a telephone (go figure)...  Called CQ with it but at this time of night the band is done for something with 8 watts INPUT.

You might say it's a baby SBE...   though it's taking up the whole bench at the moment!  

Update:  Successful test of QRP SBE rig!  in QSO with W1MPY and KB1OHJ.   Good reports. Alas, switched over to the Valiant with out making an antenna change over and arced the 6N7 tube by transmitting into it....   
Seems I may have fried the scope input that was monitoring the SBE output as well... arrgh. 

I hate self induced crapouts.

[WA1GFZ]

another fine no net control net

[WU2D]

Don't give up Ed! This morning I heard AL VTP on 75M who lives close by here in NH and this gave me a chance to fire up my PW'er. I boldly called him with the 50C5 rig which has a 4 Watt output and apparently this caused all kinds of a ruckuss. I was 10 kHz wide and mostly FM. In fact Al W1VTP was very excited because it was the first time he has used FM mode on his flex. Of course, Tim HLR Shows up (is he always listening at the exact moment things explode?) and so did Larry, NE1S both explaining how on a scale of 1 to 10 with 10 being the worst AM signal ever heard, I was hitting a solid 9!  Tim had lots of good advice of course. It is funny because the breadboard 50C5 widowmaker rig worked pretty nicely on 160 long ago when I built it before it got stored water damaged and the cat started sleeping on it. Hi.

Actually I had some shack time today so I went into troubleshooting mode and pretty quickly found that the Zener on the screen of the 12BA6 Master Oscillator (and I use that term with a dignified wink) was out of regulation, so as the voltage varied with modulation, there was lots of WOBBULATION...

Tim said that I should put the PTO (yes I have built a PTO with a wood glued coil and ferrite core attached to a knob using open construction on a board that rivals Collins) back to 160M and double up to 75M.

So I actually removed turns and increased the C radically so that I had about 700 pF on the tank and hit 160 nicely. This big  C to L ratio is another trick to increase stability.

To double up to 75M, I replaced the 2.5 mH Choke with a tuned circuit. Tim said that I needed to clean up the grid drive as well as increase it. A tuned circuit would produce more grid current, and this also might be another good thing to promote stability in the final.  While I was at it, I employed another trick that I learned with my AWA rigs that really helps simple MOPAs from pulling. That is simply to neutralize the final! Now a 50C5 does not need neutralization normally, but adding this helps the final from pulling the oscillator. I used simple Rice (grid) Neutralization with a center tapped slug coil epoxied to the board.

I also added some bypass caps to the series string AC fills in the RF section. Hopefully this would reduce the HUMULATION. This rig is a doubler off the 120VAC line with no isolation!

The final tweak was to add a steel ground plate and rubber feet to the bottom of the board. This ground plate is not directly connected to neutral for safety reasons but it is connected to the ground prong of the cord. It directly connects ONLY to the SO-239 ground plate and the bottom of the the output link. I also tagged the Heising reactor case and the mic gain pot down to the plate. The oscillator (which is at neutral with everything else) tank ground is tied to the plate with a.005 uF cap. Also near the AC cord entry, neutral and plate are connected with a 750K resistor and a .05 uF 630V cap.  
 
The result was a "1000% better signal".  Al says that I am now stable with just a hint of hum and he made some nice recordings with me on the Electrovoice 638. I checked into the net this afternoon with a more acceptable PW rig. I also checked in to the AWA net and was easily heard in Western NY with the 4W. Chock it up to good PM conditions. The schematic has been updated with the new mods! Thanks all for the help.

Mike WU2D

[W1UJR]

another fine no net control net

I made a point of hurrying back from the Westford, MA meet to get the net rolling.
We were there, but Ken DTC was holding forth on the freq. and I didn't want to bust up his roundtable.
I called in, but never really got heard.
Went up to 3880 and called CQ, no answer.

Steve WA1QIX and I were on at 4PM, and agreed that we need to have a
"Pre-net Net" to keep the frequency clear, much as we do with the Gray Hair Net.
Many of the QRO stations can't or won't hear the little QRP signals.

So look for it again next Sunday, 3PM EST, and try to get on early, to guard the frequency.

As for previous weeks, I put out a call for a alternate NCS, as I've was out of
town the last two weekends for business, first in Raleigh, NC and last week in Dallas/Fort Worth, TX.

We really need at least of couple of folks to cover NCS duties when I am away, ideally this should rotate between 2 or 3 Net Control Stations.
I've asked for it in the past, perhaps we can get 2 or 3 volunteers now, its too cool of net to let it go.

Another thought is to pick a frequency which is not subject to QRM and get everyone rocked up there.
When we are on 3880, its tough for another AM station to be on 3885 and not carry over.

[WA3VJB]

Another thought is to pick a frequency which is not subject to QRM and get everyone rocked up there.
When we are on 3880, its tough for another AM station to be on 3885 and not carry over.

Would it be much of a stretch to pick 3837Kc for these Sunday afternoons?

Seems you'd have a much better place to operate, and you'd be doing a favor to the AWA AM gathering by warming up the frequency.

Certainly no guarantee of "not subject to QRM," but there's more elbow room to deal with incompatible modes that could pop up near 3837Kc, and you're in the same propagational region as many of the AWA participants on AM.

[w1vtp]

Bruce

We were down on 3870 holding an informal breakin style session (undirected net, if you please).  Too bad you didn't notice us.

I dont have a list but Tim HLR, Mike WU2D, myself, Dale KA1WHO, Frits of Wolfboro NH  and others.  Don't remember any more as I'm having senior moment (didn't take notes as I was late myself). We went over a little bit like 4:05.  After I signed out I scurried down to the AWA AMPM net.

Tim had a 10 watt rig - Mike had a 50C5 combination with Heizing modulation that sounded pretty good. W1AEX and the worlds most ineffecient QRP rig using a pair of 3-500Z's but driving it such that it put out QRP power. I started out with 2 watts and increased to 10 after the band sagged.

Al

[WA1GFZ]

3870 got us away from Ken's buckshot.

[W2VW]

Ken just got back on after a break from a broken sky hook and a pile of snow.

He would have certainly helped you guys out if someone had tried a little harder to break in. You never know someone else's receive situation.

Ken did a bang up job at W2A with relatively low power.

He's using a smug rig so if you hear a defect please let him know......

[W1FVB]

Hi Al W1VTP. Think you mean Frits in Whitefield , NH.
It was fun checking in with you guys on 3870.
I Keep being amazed what 2 W can accomplish.
Certainly makes homebrewing a lot of fun.

73,
Frits W1FVB

[kA5WHO]

Hi Al W1VTP. Think you mean Dale KA5WHO in Wolfeboro,NH
Just foolin with ya.I did hear you Bruce throw out ur call one time,as we were moving down frequency.

73/dale/ka5who

[W1FVB]

Hi Al W1VTP. Think you mean Dale KA5WHO in Wolfeboro,NH
Just foolin with ya.I did hear you Bruce throw out ur call one time,as we were moving down frequency.

73/dale/ka5who

Maybe, I can be Dale for a Day. We can call it Double D day 

[WU2D]

Bruce, nice net today with good conditions and lots of stations checking in.

I am working on another PW AM rig. I am going to try suppressor grid modulation with a carbon mic through a transformer! That may allow me to do a true single tube AM transmitter. I am already learning that there is not much in the way of guidance other than a sample schematic couple of sentences in the handbooks. Will a high transconductance power pentode like a 6AG7 or a 5763 work? I am afraid that a proper tube like a 2E22 or 837 or 803 will crack my crystal!

Mike WU2D

[w1vtp]

Cudda sworn I hear Frits that day. Maybe it's another one of those senior moments

[WU2D]

Wow is this suppressor grid stuff is weird. First I got the XTAL oscillator running with a 6AG7 in a standard circuit like you would see for any one tube job. I got a little over 4 Watts out with 300V on the plate and 200V on the screen. The suppressor grid was grounded as usual. I built an isolated  negative power supply onto the board which doubled for - 300 VDC. Now I started introducing voltage to the grid through a bias pot and I noticed that the output started coming down. The idea is to roughly lower the output in half according to the handbooks. This has to be done while watching the screen grid current so that you do not over dissipate it. Nothing blew up so I put a 1 to 20 microphone transformer secondary with a DC resistance of 1K in series to the suppressor grid. I hit the primary with my audio generator while watching the output on the scope. Nice pretty AM came out! The audio was working against the negative voltage and causing upward modulation from the lowered carrier. Next I hooked a carbon mic and a 9V battery to the primary and said "Watson Come Here!" while monitoring. The audio was telephone quality and I was only getting about 40% modulation. So I need a bigger step up transformer LIKE A 1:40 or a better mic or both - but it works! A true one tube AM transmitter. I can't wait to QRM W1VTP.

Mike WU2D

[w1vtp]

Mike

Bring it on  .  Seriously, I'm looking forward to hearing your latest venture.  Guess you need the voltage swing.  Lemme look and see if I have anything

[Ed/KB1HYS]

Mike - that's cool!  Simple but effective.  Probably doesn't FM like the TPTG rig I'm plate modulating. 

[WU2D]

Thanks Al.

More ratio is good. I dug around and found an old TCS mic transformer which is 40:1. This iron is the real deal because it is designed to have DC and AC on both sides and it brought the modulation up to 50% or better when yelling. I will play a bit more with mic bias and such but I think I have hit the limit unless I lower the voltage on the plate. I bet a smaller tube like a 6SJ7 or 6BH6 would modulate better. The famous GRC-9 uses suppressor modulation on the final 2E24 to good effect. I will have too see how they did it.

I am using an old phone handset carbon mic. It will be on Sunday for sure. Problem is I only have rocks for 3870 and 3895.

Mike