Substituting 6146B for 2E26 in Gonset Communicator

[W3BR]

 I am working on a very clean 6 meter gooney box and I've heard stories about this tube swap being very simple. However, there are some resistor changes and power supply concerns. I am new to the AM arae so any help is greatly appreciated--Bob

[n1ps]

I have not seen such a mod and would not bother.  Even if you can get increased RF power, the single 6l6 will not be able drive it I don't believe.

You're better off improving the audio chain IMHO.

If you want more RF, find a G50 or try to locate the matching amp for the Communicator.

My .02. 

Peter

[W3BR]

Thanks Peter but this is a well known mod  , I'm just looking for assistance from someone who has experience with it..

[Pete, WA2CWA]

I've been on 6 meters since 59, and used a lot of rigs over the years, and don't recall (You said, "this is a well known mod")  any mod like this done to the Communicator series. I don't even see the point.

Now, if you happen to blow out the 2E26, in a pinch, you can probably use a 6146 as a brief sub (if it physically fit), but not as a long-term replacement. Drive circuity, driving requirements, power supply upgrade and component changes, modulator changes and probably a few other things would all have to be tweaked and diddled with in order to make it a permanent replacement. In the end, you wind up with a hacked up Communicator with very little less to show for it other then more heat and a few more watts that, most likely, someone at the receiving end won't even notice. If you want to reach out further, put up a bigger and higher antenna, or just sell the Communicator and put the proceeds toward a higher power off the shelf boatanchor 6 meter rig like the Gonset G50, Clegg Thor or Clegg Zeus.

[KX5JT]

At first I thought he just switched the tubes on accident in the title.  People will put a 2e26 where a 6146 belongs in order to drop the power out, such as in a Ranger so the carrier is down to a level more appropriate to drive a linear.  To put a 6146 where a 2e26 belongs seems really unusual. 

[w5omr]

Even if one were going to drop the output power on a Ranger to something, as John said, more manageable to drive an amp, the better way would be to drop the screen voltage on the 6146, itself. 

The problem with that on a lot of the old rigs that ran a single 6146 that was plate modulated is that the screen voltage often times is the same screen supply that is fed to the modulators.

I suppose you could add a voltage divider -at- the 6146 socket and use a heavy-duty pot that would handle the screen current when you dropped the voltage down.

[w1vtp]

FWIW  2E26 tubes are very reasonably priced on eBay.  I bought several just for grins and giggles and just in case I run across a very clean 6 meter Gooney box   
 
Al

[w5omr]

I've often thought "why not a single 2E26 modulated by a pair?"

Requirements are small - small coil, small modulation transformer - less current draw for filaments - same B+ as a 6146 - same screen voltage as a 6146... just half the dissipation.  You could make it sound freaking AWESOME, then linear amplify it up to 500w DC input or so.... or just run it QRP in your neighborhood...

[Pete, WA2CWA]

I've often thought "why not a single 2E26 modulated by a pair?"

Requirements are small - small coil, small modulation transformer - less current draw for filaments - same B+ as a 6146 - same screen voltage as a 6146... just half the dissipation.  You could make it sound freaking AWESOME, then linear amplify it up to 500w DC input or so.... or just run it QRP in your neighborhood...

How about a 6AQ5 modulated by a pair of 6AQ5's: http://www.amwindow.org/tech/htm/k1etppw.htm

[nz5n]

I ran across that 6146 for 2E26 mod while doing research about my newly acquired Gonset Communicator.  It is described at
http://www.packetradio.com/baseantennas.htm

However, I agree with the others, not worth doing.  And I do not believe it is even possible on the 2 meter version, the 6146 does not work well that high.

I have some info about Gooney Box and Twoer mods on my web page at
http://qsl.net/nz5n/TwoerGonsetRestoration.htm
Need to update that page, now have the Gonset working on FM with a PL tone board.  And just this weekend I got a 6 meter Gooney Box working.

Many of the mods, at least in my experience, proved not to be all what they claimed to be, some are definitely not worth doing.

73, Bill NZ5N

[W2WDX]

That "well known mod" is no mod worth doing and it is very incomplete and dubious at best. Firstly, I will assume you may not be familiar with AM modulating schemes since you implied that in your original post, so I will point out some things very plainly.

First, the power increase will be marginal. An increase in carrier power from 7-10 to 14-20 (or so) watts is not even noticeable on air. You may not even see that increase due to limits in power supply capability in the Gonset. Besides that, driving an amplifier for six meters you are better off at the 10w range anyway.

Second, the modulator in the Gonset barely has enough power to modulated a single 2e26 at 7 watts PO. It is hard pressed and has high distortion at 95% modulation. It will only modulate a 6146 to about 45%, much too low for low power AM operation. It is possible to "hot-rod" everything, but why do that? The modulation transformer used in the Gonset already begins to saturate at the 3-4 watt max level the modulator runs at, one of its design limitations.

Thirdly, the Communicators were designed to be small lightweight emergency transceivers, so the power supplies were reduced to the smallest they could be for the circuits being used. Good regulation is even a problem with the original circuitry and its current draw. I do not think increasing that current draw will be a good thing for regulation, distortion products and linearity, and especially reliability.

There are limits with any design, and the Communicator is already running near or above those limits. Simply increasing carrier power will force a change in the design in every aspect of the radio; supply voltages, current capacity of the PSU, larger chokes, a total redesign of the modulator including the mod transformer (which will make using the receiver audio impossible since its shared & proprietary, BTW), etc. Essentially, you will have to change every circuit in major ways to get the Communicator to work even reasonably well to gain 7-10 watts more of carrier, especially in the modulator. Not to mention there is just enough room in the Gonset for the size of the rated components. Adding larger parts or more parts, especially in the modulator/RF deck chassis and the PS chassis, may be physically impossible.

Something to remember about AM especially when running low power; its all about audio quality and intensity. Lower carrier power, high modulation levels with high RMS values. With high carrier power (200w carrier or higher) you can get away with lower modulation levels and lower RMS values, but many run near 100% or even higher with high carriers regardless. And this becomes even more important when you are running VHF when you take into account higher general losses, less support from propagation and limits thereof, and line of sight limitations.

You would be much better served by improving the basic audio quality (even adding a line level input and using external audio processing to achieve higher audio RMS values) and driving a small amplifier when using a Communicator.  If you really want more power, why not try to find the Gonset amplifier that went with the radio? It's a neat little amp. Or use a brick. A nice 160W amp designed for a 40 watt drive would be perfect for the Communicator, and if you use an over rated DC power supply it will run with decent linearity on AM.

John W2WDX