Re: Topband: 160m monoband amp (was strange propagation)
Thanks Mike, I'm not going anywhere. I hope that Tom reconsiders his leaving. If you look at the time and effort he spent on his website which he always updates and adds to, and the efforts he puts forth on the various reflectors you have to say it is nothing less than admirable. A handful of people do such things and many of them are on here also. So I agree, this is the place to be. I've know about this reflector for years but never bothered with it since my interest in 160 was nil. Recently I made a decision to give it a crack and boy do I see it is a whole lot different than working even 80 meters and above. Lou W1QJ -Original Message- From: Mike Waters <mikew...@gmail.com> To: Louis Parascondola <gudguy...@aol.com> Cc: topband <topband@contesting.com> Sent: Sat, Jan 16, 2016 7:40 pm Subject: Re: Topband: 160m monoband amp (was strange propagation) Hi Lou, Of all the sources of unique help and info about 160 meters, IMO this reflector is the best one. I suppose you've found the searchable archives, which I've found invaluable many times: lists.contesting.com/archives//html/Topband/ lists.contesting.com/archives//cgi-bin/namazu.cgi?idxname=Topband There are other sources, notably ON4UN's Low Band DXing, published by the ARRL. Everyone with an interest in 160m should own a copy. There are a number of other informative web sites out there, too. I have some of them listed and linked to from www.w0btu.com (not all on one page, sorry). And there's a page there about Beverage antennas there that you might find useful. Maybe you would let me pick your brain sometime about my swamped-grid dual-833C legal limit amp. It works fine on 160 and 80, but it needs neutralizing if it's going to be stable on 40 (and work at all on 20). I have a plan to neutralize it using a tertiary winding on the input transformer, but I foresee a lot of trial and error. But I don't have time to work on that right now. I wasn't even sure if two of those triodes in parallel would even work, so I didn't spend a lot of time making it look pretty. www.w0btu.com/833C_linear_amplifier.html Stick around, Lou. Believe it or not, this is usually a friendly forum! 73, Mike www.w0btu.com On Sat, Jan 16, 2016 at 9:31 AM, Louis Parascondola via Topband <topband@contesting.com> wrote: I came to the group to try to pick up pointers on improving my 160 meter experience. In the short two weeks I have been here I have so much information to digest. Especially with receiving antennas, _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: 160m monoband amp (was strange propagation)
Hi Lou, Of all the sources of unique help and info about 160 meters, IMO this reflector is the best one. I suppose you've found the searchable archives, which I've found invaluable many times: lists.contesting.com/archives//html/Topband/ lists.contesting.com/archives//cgi-bin/namazu.cgi?idxname=Topband There are other sources, notably ON4UN's Low Band DXing, published by the ARRL. Everyone with an interest in 160m should own a copy. There are a number of other informative web sites out there, too. I have some of them listed and linked to from www.w0btu.com (not all on one page, sorry). And there's a page there about Beverage antennas there that you might find useful. Maybe you would let me pick your brain sometime about my swamped-grid dual-833C legal limit amp. It works fine on 160 and 80, but it needs neutralizing if it's going to be stable on 40 (and work at all on 20). I have a plan to neutralize it using a tertiary winding on the input transformer, but I foresee a lot of trial and error. But I don't have time to work on that right now. I wasn't even sure if two of those triodes in parallel would even work, so I didn't spend a lot of time making it look pretty. www.w0btu.com/833C_linear_amplifier.html Stick around, Lou. Believe it or not, this is usually a friendly forum! 73, Mike www.w0btu.com On Sat, Jan 16, 2016 at 9:31 AM, Louis Parascondola via Topband < topband@contesting.com> wrote: > I came to the group to try to pick up pointers on improving my 160 meter > experience. In the short two weeks I have been here I have so much > information to digest. Especially with receiving antennas, > _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: 160m monoband amp (was strange propagation)
I came to the group to try to pick up pointers on improving my 160 meter experience. In the short two weeks I have been here I have so much information to digest. Especially with receiving antennas, which in my short time here has proven to be "the secret weapon". If you can't hear them you can't work them. Since I know little to nothing about these antennas I can't offer any help to anyone. I am usually one that likes to contribute but I certainly can't contribute a single thing about these types of antennas and feedlines. So I can only do the next best thing. I'd like to share my experience with taking a couple of flea market basket case amps that I converted to mono band 160 meter amps with some surprising results!! I am one that usually looks for the stuff at hamfests that doesn't work rather than some expensive stuff that I would gamble my money on. So in the course of many years of perusing hamfests I picked up some basket case amps. Two specifically that come to mind are a well beat up and chopped up Heathkit SB-200 and a Dentron Clipperton L, They had missing band switches and tank circuits chopped for CB or whatever. I know that many hams don't use amplifiers on the higher HF frequencies, but some many consider that the extra power could be of benefit on 160.So I decided to do a conversion on the other end of the spectrum from 6 meters. I started out with the SB-200 and gutted it out completely and started with a clean slate. Cleaned up the years of crude and went to work on a mono band 160 meter amp. I scrounged all the parts from other amps that had been taken apart for various reasons. The first thing I did was to upsize the filament choke with a higher inductance, a unit from an old SB-1000 I believe fit nicely. A typical unit found in an AL-80B can be bought direct from Ameritron pretty cheap. One of the things I found in the junk box was an nice heavy duty toroid that came from a Viewstar PT-2500 amp. I deci ded to use this to make a toroid tank circuit inductor instead of a open air coil to reduce the overall size. Using the guidelines in the handbook I started at a tank inductor value that was close to calculation. I rewound a coil on the toroid core and measured it. It was very close to calculation so I installed it. I then worked up pi-net input circuit using an adjustable coil like in the original SB-200 and some mica caps. I used values for both inductor and caps (to begin with) from some of the commercially made amps. I put this all together and gave it a whirl to see where I was at. To my surprise I was pretty much in the ballpark. A bit of tweaking on the input circuit and I soon had a nice flat input swr. In amp building the input circuit should be just as important as the tank circuit. The more efficient the input circuit the better the amp will perform power wise. This seems to be a place where many do not spend enough time on. Once I got the input circ uit perfect I plotted the output across the band and adjusted the tank coil for best results on the lower end of 160 meters. When I tweaked it all up I was rather surprised as to the performance. The SB-200 runs a pair of 572B tubes and like most thoriated tungsten tubes the limiting factor is grid current, well that could be said for just about any transmitting tube, anyhow loading the amp up into a dummy load and using the "white area" on the SB-200 meter as a guideline which relates to 200ma, I drove the amp and topped off the power right on the edge of the white line. The power output was an honest 900 watts. You have to understand that when you remove all the switching and compromise from a multiband amp and create a mono band amp, you increase the efficiency quite a bit, as can easily be seen here. I did a "key down" test for about 20 seconds straight and the tubes did not show any appreciable overheating of the anode. This usually proves that the losses are mini mal and the anode is giving off its power to the load all of which points to a good tank circuit. Trying to load into an improper load is quickly indicated by rapid anode heat, hence very red anode color. I neglected to mention that I did pad the load and tune caps using values from the handbook to begin with and then tweaking so that I had sufficient travel on each variable cap to compensate for varying loads. Running this amp at 800 watts would be a snap and for simply calling in pile ups full power shouldn't be a problem. Now as for the Clippetron L, I did a 160 conversion on that one also. On this one I wanted to try an air wound coil, so I followed the same procedure as the SB-200 for calculations and put together an input circuit as before, once again using a starting point of a similar amp running 4 572B tubes The AL-572B would be what I probably used to start. I wound an air wound coil using heavy duty #10 enamel wire with the inductance I got
