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Post by rocks on Jun 10, 2023 10:31:01 GMT -5
Glad to find this forum and thank you for taking the time to read over my post. The radio in question is putting out 3 watts, works well here around our area.
Its antenna is a vertical antenna, the SWR is flat and like I say it’s running well. I adjusted the plate and load to get it where it’s at from 2 watts. Any suggestions to get its full 4 watts on am, I do have a bunch of tubes and a tester, thought I may start there.
Please advise, name is Rod.
Thank you.
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Jun 10, 2023 20:52:04 GMT -5
Glad to find this forum and thank you for taking the time to read over my post. The radio in question is putting out 3 watts, works well here around our area. Its antenna is a vertical antenna, the SWR is flat and like I say it’s running well. I adjusted the plate and load to get it where it’s at from 2 watts. Any suggestions to get its full 4 watts on am, I do have a bunch of tubes and a tester, thought I may start there. Please advise, name is Rod. Thank you. Radios made before the mid 70's were spec'd by input power rather than output power. When your radio was made the spec was 5 watts input. That translated to roughly a 3 watt output. So your radio is performing to manufacturer's specs at the time of manufacture. That being said, there are modifications that can be made to boost power. But those usually come at the expense of audio modulation. In the grand scheme of things no one would ever notice the difference between 3 and 4 watts. |
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Post by rocks on Jun 10, 2023 22:31:58 GMT -5
That’s some good news thank you! I’ve been out in the vehicles and the radio does sound good. The family here has had quite a bit of fun with it.
I do have a couple more tower pieces that would put the antenna up another twenty foot. I also have a 3 element beam that will tune up on 11 meters.
I sure appreciate you jumping in here and setting me straight. 73 from Utah.
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Post by 2600 on Jun 11, 2023 1:01:24 GMT -5
The "four Watt" rule came about after solid-state CB radios took over the market. Before that, the FCC rules specified a number called "input" power. This is the high-voltage feeding the final tube multiplied by the DC current the tube draws. Was specified at 5 Watts INPUT power. This is an obsolete way of measuring transmitter performance. Ham radios at the time were limited to what the rules called 1000 Watts of input power. We'll skip the historical story of why the FCC used this measurement in the rules, but in the late 70s/early 80s they updated the CB-radio power limit to the OUTPUT RF power. Rounded it off to 4 Watts. The final amp stage in a solid-stage CB tended to be a little more efficient, and would get you 80 percent of that 5-Watt "input", or 4 Watts output. Efficiency for a tube final will be closer to 60 or 70 percent, getting you a 3 or 3.5 Watt carrier with that 5 Watt input side.
Tube radios are just different. Bigger, more expensive tube base radios will deliver more than this, especially the ones built to run single sideband. But the Mark 2 is probably giving you all that it can without upgrading or modifying the power supply. There is not much to be gained by "hot-rodding" this transmitter, so I'll skip the how-to on that. Besides, an extra half Watt or even a full Watt increase would not be enough to see on the receiver S-meter at the other end of the conversation. A receiver's S-meter responds very differently than your wattmeter. Boosting this transmitter is strictly a "feel good" improvement that won't change who hears you or who doesn't.
If you're just obsessed with the idea, you may find that swapping the final and modulator tube will show power differences of a half Watt, maybe more. Maybe no difference at all.
Oh, and when the wording of the rules was changed for hams, it became an upper limit of 1500 Watts PEP RF output power.
73
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Post by rocks on Jun 11, 2023 6:26:24 GMT -5
Thank you for sharing this information with me about my radio, I just thought it wasn’t quite up to snuff and maybe I could do something with it easily. At this point I see no reason to mess with it and fill quite lucky it’s running as well as it is.
I do have another one boxed up and several tube type radios I’ve messed with over the years. This one’s been the most fun for us all I must say because all of us jump in and run the thing.
What a wonderful group you all have here, and I’ll keep reading over as much as I can for the next few weeks.
Rod
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