1 watt AM on 40 ain't gonna cut it...

[VE3GZB]

I'm going to have to raise power/rebuild this QRP rig until I get the bigger Xmitr up and running.

The 1 watt I can get is with zero modulation/full carrier. To modulate it (fixed output Heising modulator) I have to reduce the carrier and watch the envelope on the scope.

How much power would work for QRP AM on 40? Any recommended minimum power levels?

Thanks and 73s
geo

[WA3VJB]

Daytime without a lot of congestion, a couple dozen watts has been fine for the stations I work 400-800 miles distant.

Nighttime or when the band is turning, you'd want more margin.

[VE3GZB]

Yea, it would be night time (only on weekends could I run at daytime).

20 watts then, you say?

Thanks!

[W2PFY]

How much power would work for QRP AM on 40?

I have worked WA1HLR on his QRP 1/2 watt transmitter on 40 meters in the past. He had all his audio processors hooked to it and it sounded as good or better than his BC-610B. I think that for most daytime AM you can easily have a lot of fun with less than 100 watts.  I have had many contact on 40 using 5 watts

[WA3VJB]

A lot of it depends on your antenna. If the design is effective for the region you wish to cover at night, scale the power accordingly. 40m propagation really varies at night, where I've found a couple hundred watts sinks without a trace sometimes. 

Yea, it would be night time (only on weekends could I run at daytime).

20 watts then, you say?

Thanks!

I've worked mobile stations daytime where they're using a couple dozen watts.

[VE3GZB]

1/2 watt?? Impossible! The antenna must be unbelievable! I've heard of such stories, I remember reading of these kind of things as a youth, but it seems impossible to me given how much noise is out there.

My antenna now is an inverted V hung from the top of the old unused Yagi off the TV tower. It's a big improvement - so I have been told and shown with a 110 watt SSB rig connected to it.

Hmm, this is going to require more data/research before I scrounge and devote resources to a QRP AM rig (until the big one is running again, still waiting on modulator tubes for it).

73s,
geo

[W2PFY]

/2 watt?? Impossible! The antenna must be unbelievable!

Well Tim is a lucky guy, most of his antenna are up near 190 feet on six broadcast or communications towers that he has leased out to people on HLR mountain. There are more than six towers but they are not as tall. Here on the receiving end, it's very quiet except for the occasional horse fart reverberation off the near by mountains. Most people would pray to have such an RF quiet place as this and I'm not kidding, no RF noise except what I create 

[Ed/KB1HYS]

Antennas make all the difference.  for those of us who can't have the plus-ultra antenna farm there are Eimac Products....
a QRP AM rig could be simple.  You could "drain" modulate a pair of IRF510's in PP with anothe pair and a power transformer as mod tranny.

Look up the MiniBoots amplifier. Its a QRP class C amp based on the IRF510.  You could modulate its voltage with a reversed output transformer and an off the shelf audio amp.  get maybe 5-15 watts out depending on the power supply etc.

It's something I've been thinking about, but I'd rather finish up the QRO project

[WU2D]

I ran a 2N2222 on 40M back in the 1970s with an ordinary dipole and RG-58 and made all kinds of contacts with a couple hundred milliwatts. But these were strictly during the day on single hop east coast stations, not at night.

Then I built a 1 Watt CW rig and this worked even better.

You need a few more dB to work 40M at night these days.

5 Watts out would be a start for CW. Gosh a 6AW8A with the triode as a crystal controlled Pierce and the Pentode side as the Final would be a simple rig. Here are a couple of examples of some clean 40M CW rigs using the common tall 9 pins.

Mike WU2D

[WU2D]

It would be a cinch to high level modulate these with a pair of 6AQ5's and a 12AX7 driver.

Then you would have a 5 Watt AM rig - Hi

Mike WU2D

[VK7ZL]

I run a QQE03/12 wired as a single tetrode and get 7W out on 40M. The antenna is an Inverted V at 30' and I can work station up to about 500 miles when conditions are reasonable.

Bob

[VE3GZB]

I'm going to rebuild, I'm going on a budget parts expedition tomorrow down to Toronto, stopping in at A1 electronics to see what I can get for $20. Hoping for some old chassis I can harvest parts from!

I found two 6BG6 tubes and two 6N7 tubes in my junkbox - I don't have many tubes, I used to long ago but that's another story - and I can supply 6.3V.

I'll only use one of each to form the RF portion of another transmitter and try screen modulation to get my voice on the air.

Hopefully I can develop 20-30 watts.

73s
geo

[N0WVA]

I had a one watt solid state rig on 75m back in the mid 90's. Worked good, I modulated both the driver and final, to a very good antenna, and with a VFO. I remember a station in Tulsa, was it John? He didnt believe me, and seemed like a jerk. Not sure if hes still around, maybe a silent key. I dont have my log and cant remember the callsign, only that he presumed I was lying.

[Knightt150]

Hey: What dose WA1HLR 1 watt rig look like and can you purchase one. I am very interested in low power AM, has anyone modified a Heath Kit HW8 to operate AM I have one of those.

John W9BFO

[Carl WA1KPD]

I ran a 2N2222 on 40M back in the 1970s with an ordinary dipole and RG-58 and made all kinds of contacts with a couple hundred milliwatts. But these were strictly during the day on single hop east coast stations, not at night.

Mike WU2D

Mike,
I did to. Was it the Tuna Tin Two? I had a blast with it. My best contacts were right with the gray line.
Best DX was Ct to Ill about 4:30 pm this time of year

[n1exi]

for years i've run 4 watts output on 75 and 40 meters  - nothing fancy for antennas either - bent dipole on 75 and inv for 40 - key is lotsa modulation and right times -early am and pm when qrm is low
Greg

[W2PFY]

Hey: What dose WA1HLR 1 watt rig look like and can you purchase one.

You would have to contact Tim, Maybe he would build you one. Send him a PM on this board. I wish you luck on getting a response as Tim rarely checks in here or responses to emails. This is not an attack on Tim, you would be better off writing him a letter with your phone number in it.