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 Post subject: Increase power of Clegg 99'er?
PostPosted: Jan Wed 03, 2018 5:07 am 
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Location: Raleigh, NC area
An article I found online from the June, 1968 edition of Radio Amateur discussed increasing the power output of the Clegg 99'er. I get roughly 4W out of mine on the carrier, and would like to get out a bit louder. Already have tried several antennas, including two beams, which work pretty well.

https://www.radioexperimenter.us/rm-1968-06/v-mjw.html

The article mentions replacing the 6BW4 rectifier with Sylvania F8 silicon diodes, to increase the B+ across the board. What might be the modern equivalent to these diodes? Or, do I just need to find something that will handle the inverse voltage? Not a lot of current here.

The article also mentions decreasing the screen grid resistor of the final (7558) from 33k to 10k, and increasing the mic preamp output. The author states these changes had been in place for five years on his set, with no known issues.

The modifications supposedly take the input power from 8W to 15W. Don't know what the output power gets to, but could be about 7W(?) Do you see any issues with this? This isn't a collector quality set, so I don't have concerns there.
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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Wed 03, 2018 1:19 pm 
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The biggest concern would be the power transformer so keep your transmission length reasonable. A pair of 1N4007 rectifiers will be fine for the power supply.

Although doubling of power sounds like a lot you are gaining only 3 db. Typical ham receivers are calibrated so that each S meter unit represents an increase of 6 db so doubling your power gains about half of an S unit on the receiving end or basically not enough to be noticed.

You made a good decision already by using a beam antenna which benefits both receive and transmit operation and make sure you are feeding it with good low loss coax. To gain a further major increase in transmitter performance you will really need an external amplifier that will handle AM and get you into the 200-300 watt input range. Six meters is low enough in frequency that care but special construction techniques aren't needed and a single band amplifier isn't difficult to build since it is nothing more than a single high power stage. Some of the better built external power supplies for 60s/70s era transceivers can be used for the power supply if you choose the proper tubes for the amp so that the amp may be able to share a power supply that you already own.

Rodger WQ9E


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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Wed 03, 2018 1:44 pm 
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Location: Raleigh, NC area
Thanks Rodger. I knew the measly 3dB was about all I would get and that wouldn't be as much as the antenna improvements. It just seemed like a pretty easy modification to do for the Clegg.

I've thought about an amp. I only use this for the local 6M AM net. The other 99.4% of the time (literally), there's just nothing there but static. Can't do other modes with the 99'er, so hardly worth building or buying an amp, I think. For that matter, if not for the darned allure of the TUBES, everything is easily solved with a relatively inexpensive, used, modern, all-band rig. Which kind of defeats the purpose...


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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Wed 03, 2018 1:54 pm 
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I agree the amp wouldn't be worthwhile if limited use for local contacts on 6 meter AM is all that you want. 6 is an interesting band and it will have sporadic openings but often there isn't much AM activity during those openings. But if you have a good antenna for 6 you might find operating on all modes interesting and once you go to a 6 meter all mode then an amp that you can use both with it and the Clegg 99er starts to make more sense.

If you want to stay somewhat vintage but have all mode capability for 6 meters then a Kenwood TS-600 isn't a bad choice. The Drake TR-6 (basically a low power 20 meter transceiver with 6 meter transverter built in) is a nice medium power all mode but somewhat scarce and pricey.

I have a Johnson Thunderbolt 6N2 amp but haven't used it past the bench testing phase yet because the 6 and 2 meter beams I have around aren't rated for that kind of power and I am not a big 6 and 2 meter op.

Rodger WQ9E


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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Wed 03, 2018 7:29 pm 
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The Clegg 99'er is a "cute" 6 meter vintage transceiver but there are many other vintage 6 meter tube transceivers that can run more power. In the Clegg line, the Clegg 66'er and the Clegg Thor are great transceivers that run more power. The Lafayette HA-460 is also a very popular 6 meter transceiver.

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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Thu 04, 2018 1:01 am 
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Location: Raleigh, NC area
manualman wrote:
The Clegg 99'er is a "cute" 6 meter vintage transceiver but there are many other vintage 6 meter tube transceivers that can run more power. In the Clegg line, the Clegg 66'er and the Clegg Thor are great transceivers that run more power. The Lafayette HA-460 is also a very popular 6 meter transceiver.


Thanks... Yeah, it's "cute," but was also free, aside from the new tubes I put in it. The other rigs mentioned are scarce and usually pricey if in working/good condition, and often even if not. Signs of the much improved economy I guess. "If I can hear them I can work them," even with my 3rd floor attic beam, and the 99'er, unless their own beam is pointing in the other direction (and sometimes even then). It's actually a pretty decent 6m rig for a mode and band hardly used any more. I don't doubt the other mentioned rigs are better, but this is what I have.


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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Thu 04, 2018 1:28 am 
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Dave,

Maybe this is a case where you keep your eyes open for a cheap but not completely blown up tube type "CB linear". I expect most of the two tube types could be fairly easily rolled into a 6 meter amplifier and your rebuild would likely be better than the initial build. Drake used three sweep tubes in parallel for the TR-6 and they play fine on 6 meters. I suspect the Knight T-150A could have been a decent 6 meter rig with its pair of 6146 finals running controlled carrier AM but the rig doesn't produce nearly enough grid excitation on 6 meters so power input is poor and output, due to lousy efficiency, is horrible on that band. It is sort of like operating the Harvey Wells TBS-50 on 2 meters; it does produce just enough output there that H W could claim 2 meter operation :)

I vaguely recall one of the WRL rigs had an add-on accessory to provide better drive and power on 6 meters and clearly the T-150 needed something like that also.

Keep an eye out at hamfests and sooner, rather than later, you should find a more powerful 6 meter rig at a good price. Outside of the collector pricing on ebay there isn't a lot of demand in most areas for a 6 meter AM rig so they tend to attract nostalgic attention at hamfests but not so many offers. My nice looking Gonset G-50 set me back $25 at a small hamfest and I passed it multiple times before deciding to buy it just before leaving. It runs 48 watts input to a 6146 final modulated by a pair of 6L6 tubes. A Johnson Challenger will run around 70 watts input on 6 meter but this is not one of Johnson's better efforts.

Rodger WQ9E


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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Thu 04, 2018 3:21 pm 
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Hey in a free radio, I might just go ahead with the mod, simply because you get rid of a heat generating rectifier tube, and one less to replace, even with the side benefits. But for the transmit mods, I would like to have a power meter and a scope, just so I could check the output and the modulation for distortion, etc. to see if it really does do what he claims. Like, can the modulator generate the extra power output to modulate the higher carrier value, without clipping, etc? I doubt the mag editors made them prove the mods work correctly other than taking his word. Often it depends on the rep of the writer. And the mag. Ham rigs adverts use the specs wars to gain market, so you might consider why Clegg did not make simple changes to get a higher number for higher sales considerations. And running that tube harder in the output. How easy are they to get? On the plus side, if it works fine, you get expeirence with mods, working on that particular radio and if it works, no harm no foul.

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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Thu 04, 2018 6:08 pm 
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Location: Raleigh, NC area
rsingl wrote:
Maybe this is a case where you keep your eyes open for a cheap but not completely blown up tube type "CB linear". I expect most of the two tube types could be fairly easily rolled into a 6 meter amplifier and your rebuild would likely be better than the initial build. Drake used three sweep tubes in parallel for the TR-6 and they play fine on 6 meters. I suspect the Knight T-150A could have been a decent 6 meter rig with its pair of 6146 finals running controlled carrier AM but the rig doesn't produce nearly enough grid excitation on 6 meters so power input is poor and output, due to lousy efficiency, is horrible on that band. It is sort of like operating the Harvey Wells TBS-50 on 2 meters; it does produce just enough output there that H W could claim 2 meter operation :)

Thanks Rodger. You are a good order of magnitude more capable than I in this regard ;)

rsingl wrote:
My nice looking Gonset G-50 set me back $25 at a small hamfest

You did quite well with that...


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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Thu 04, 2018 6:15 pm 
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wazz wrote:
you might consider why Clegg did not make simple changes to get a higher number for higher sales considerations. And running that tube harder in the output. How easy are they to get?


Both good points. I was also wondering why Ed Clegg didn't do this. I figured one of three reasons: the stress on the components as you noted; or cannibalizing sales of higher end; or targeted for mobile use, and keeping input power down (and heat) might have been a concern.

I do have a scope and a Knight CB checker which can measure power, though not known how accurate it is at 6m.


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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Jan Fri 05, 2018 9:22 pm 
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DaveInNC wrote:
wazz wrote:
you might consider why Clegg did not make simple changes to get a higher number for higher sales considerations. And running that tube harder in the output. How easy are they to get?


Both good points. I was also wondering why Ed Clegg didn't do this. I figured one of three reasons: the stress on the components as you noted; or cannibalizing sales of higher end; or targeted for mobile use, and keeping input power down (and heat) might have been a concern.

I do have a scope and a Knight CB checker which can measure power, though not known how accurate it is at 6m.

Since I’m older then dirt, I had the pleasure of personally knowing Ed Clegg and also had the opportunity to see the Clegg 99’er production assembly at their Mt Tabor facility.

Most good design engineers during the vacuum tube period tended to use the manufacturer’s tube design specifications and tube charts to determine the necessary and “good” operating parameters. Designing at the edge of manufacturer’s typical design parameters tends to shorten tube life, may cause circuit instability, may put circuit components at risk of failure, and may cause operating deficiencies. Mods, on the other hand, sometimes forgo many of these types of risks when pushing the design parameters beyond the recommended criteria.

You probably could get an additional edge by not modifying the RF section but by adding a simple audio diode clipper to the modulator. It would increase your AM “talk power”. Five watt CB sets used them for years.

6 meters may not be used that much for AM some of the time, but overall it's a very popular and used band for many of the other modes. 6 meters is even used to do EME using CW and digital modes.

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http://www.classicradiomanuals.com


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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Feb Wed 21, 2018 3:07 pm 
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I've recently looked at a couple of 99'ers and they both had one big problem: insufficient modulation. One of them had the lower grid resistor value on the final, in this case about 11K. The output power was a few watts higher, but I suspect the 7558 will not enjoy a long, productive life. This also seemed to exacerbate the problem of the modulator not being able to provide enough clean audio to get anywhere near 100% modulation. Unless you're planning to turn your 99'er into a CW rig, having a stronger carrier with weaker audio will not get you to the promised land. I ended up changing the grid resistor to 56K (the other rig had the stock 33K value) and saw a significant improvement in modulation. This also lowered the grid current on the 7558 from about 6ma to about 2.5ma so much easier on the final.

Another problem on both radios was that the TX response peaked at 500Hz, hardly rolled off at all on the low end but was down almost 10dB at 3KHz. I played with some of the coupling and bypass cap values and improved things quite a bit, although it's not exactly "high fidelity". If you want more detail on any of this, let me know.

Replacing the 6BW4 with a couple of 1N5404 (or 5405 - 5408) is worth doing. It raised the B+ in my rig to up over 300 volts and that did provide a noticeable increase in output power (measured on a meter, your mileage may vary). My rig also has a nuvistor cascode RX preamp that a previous owner installed. It sounds great and seems to be almost as sensitive as the receiver on my Kenwood TS-590SG.

My 99'er is connected to a 40 meter dipole at 55', resonant close to 7MHz and fed with 110 feet of LMR-400 (VSWR ~ 1.5:1). I use it for our local weekend morning net and have no problem working stations within about a 25 mile radius.


Last edited by WA8WGN on Feb Wed 21, 2018 11:23 pm, edited 1 time in total.

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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Feb Wed 21, 2018 9:38 pm 
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WA8WGN wrote:
I've recently looked at a couple of 99'ers and they both had one big problem: insufficient modulation. One of them had the lower grid resistor value on the final, in this case about 11K. The output power was a few watts higher, but I suspect the 2E26 will not enjoy a long, productive life. This also seemed to exacerbate the problem of the modulator not being able to provide enough clean audio to get anywhere near 100% modulation. Unless you're planning to turn your 99'er into a CW rig, having a stronger carrier with weaker audio will not get you to the promised land. I ended up changing the grid resistor to 56K (the other rig had the stock 33K value) and saw a significant improvement in modulation. This also lowered the grid current on the 2E26 from about 6ma to about 2.5ma so much easier on the final.

What 2E26?

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 Post subject: Re: Increase power of Clegg 99'er?
PostPosted: Feb Wed 21, 2018 11:05 pm 
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Ahh, sorry I meant to say the 7558! Am also working on a Lafayette HA-460 so my old brain musta got confused...


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