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Author Topic: Cost of Building an HF Amplifier?  (Read 4444 times)
MM0IMC
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Posts: 255




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« on: February 04, 2019, 06:11:52 AM »

Just curious, if I want to build myself an HF amplifier based around Russian NOS Ceramic valves (tubes), how much would it cost in comparison to a commercial build amplifier? Would it be any cheaper?
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KU3X
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« Reply #1 on: February 04, 2019, 07:13:01 AM »

My first amplifier used a pair of 4-400 AX tubes. The total cost of the amplifier was less than $500. But a lot of parts were donated to me as well as a lot of used parts from hamfests.
If you have to purchase all of your parts new, it's probably not worth it unless you just like building.

If you do build it, there is a sense of pride. I've built numerous home brew amps. I learned a lot since I had to do it totally on my own. I had no help what so ever from anybody.

Barry
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KS2G
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« Reply #2 on: February 04, 2019, 09:14:26 AM »

Just curious, if I want to build myself an HF amplifier based around Russian NOS Ceramic valves (tubes), how much would it cost in comparison to a commercial build amplifier? Would it be any cheaper?

Put together a parts list and start pricing.

My guess is that you probably can purchase a comparable new commercially-made unit for less.
Almost certain that a second-hand unit will be cost less than what you can home brew.

Also, what's your time worth?

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AB5NI
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« Reply #3 on: February 04, 2019, 09:20:14 AM »

Personally, I like building my own gear. The great thing about doing it is that you can fix it yourself -- you know the design inside out. OTOH, if I was going to go the frugality route, I might look into purchasing a GLA-1000, removing the sweep tubes, and replacing them with NOS Russian tubes. Numerous examples of doing this can be found on YouTube. I guess you could always piece one together, purchasing necessary components from hamfests, friends, and so forth. The best thing about building your own amp is the learning experience.

Another route, as for as frugality goes, would be to build a B+ supply from a MOT (Microwave Oven Transformer). There are quite a few examples on how to do this on YouTube as well.

The last and final option, IMHO, would be to purchase a CB amplifier that uses "pills" (LMAO!) and add some lowpass filtering, but that option would require a stout, 12V power supply. Where there is a will there's a way Cheesy.

73,

Randy AB5NI
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I eat spaghetti code out of a bit bucket while sitting at a hash table, and I pay for the meal with cache!
W1VT
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« Reply #4 on: February 04, 2019, 09:33:37 AM »

I've heard that it is hard to find a suitable high voltage transformer for a tube amplifier in the UK, so  you may want to investigate that first.
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KD7RDZI2
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« Reply #5 on: February 04, 2019, 12:03:55 PM »

Same question I asked to some hams that actually built a PA at my local radio club. They all agree that as for reasonably priced high power stuff like Acom, OM Power you would spend much more building yourself, and they are very well built. I guess also for many Ameritron is the same thing, the 811 included. There is valuable stuff in a PA, and a lot of work. I am not a fan of amplifiers, for just 10-13db gain there are significant costs and in my opinion 100W should be enough to have a dx qso, WRTC teaches something, but I admire how good these PAs are built, to last decades. My guess is that margins are higher for low power amplifiers made for QRPs (say from 5 to 100)... there the price per watt may rise considerably and are relatively easy to build yourself.
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N8CBX
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« Reply #6 on: February 04, 2019, 01:54:22 PM »

...I want to build myself an HF amplifier...
The cost of amp materials isn't that important for your first amp build. What is important is knowledge. What is it going to cost (in dollars & time) to get the knowledge & experience to build your first amplifier?
My recommendation, for the very first thing to do, is to acquire documentation on the web and/or get a Bill Orr authored handbook. I suggest the 23rd edition.
Jan N8CBX
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Dayton Ohio - The Birthplace of Aviation
N8CBX
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« Reply #7 on: February 04, 2019, 08:25:41 PM »

One needs test equipment to test the circuits that one builds. You're going to need electronic bench stock (caps, resistors, and so on...on-hand) as well.
I use the best materials and so on. That's one of the advantages of homebrewing is that you can conservatively build the circuits with the best. Amplifier vendors build their products....well, to sell and to optimize their profits! So, they "minimize" the amount & price of parts. Which is okay if you just want to buy it plug-in-play & ready-to-run.
The feeling of satisfaction of building your amplifier is awesome...as they say. And you LEARN one-hell-of-a-lot too!
Jan N8CBX
« Last Edit: February 04, 2019, 08:28:22 PM by N8CBX » Logged

Dayton Ohio - The Birthplace of Aviation
W1VT
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« Reply #8 on: February 05, 2019, 07:52:24 AM »

You may want to check with local radio clubs to see if there are any local hams that have parts they would give to you.  Older hams should consider downsizing their estate of non-salable items to ease the burden on their loved ones.
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N8CBX
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« Reply #9 on: February 05, 2019, 08:39:48 AM »

Also to mention on parts sources, I buy a lot of parts from Ameritron/MFJ. And their amplifier layouts are good examples for your homebrew amp.
Jan N8CBX
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Dayton Ohio - The Birthplace of Aviation
G3RZP
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« Reply #10 on: February 06, 2019, 01:48:49 AM »

Depends how far you want to travel and exactly what you want. I have a number of HV parts that can go, such as a 3200 volt 1.2 amp 230volt primary transformer and a choke and suitable paper caps for tuning it and a big paper cap suitable for filtering, plus a 200 watt bleeder resistance. But would need collecting from Wiltshire. And a 500pF 7.5kV vacuum variable.
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N4HZ
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« Reply #11 on: February 06, 2019, 06:23:20 PM »

I've built two amplifiers.  The first is  4-1000 amp using a lot of free parts and probably only have a couple hundred dollars in it.  My second home brew is a standard two tube 3-500 amp which I built using a tool chest as the container.  That one I bought almost every part.  Total cost of the build was $1400 even with some used parts from eBay.( and I only built for 75,40 and 20 meters)  I had the HV transformer built for $400, the tool chest was about $100, the two tubes around $350 if I remember correctly.  I made a manual for the amp including schematic, test data, theory of operation and a page with every part cost and have it on my computer.  I would post the parts page but am having trouble getting it to post due to the columns getting scrambled.   Anyway, small things like sockets,HV wire, relays, meters,  ( I used four and made custom scales) tune/load caps, etc. add up.  My view is that if cost is the driver it is much more practical to buy a good used amp.  However,  as others have mentioned there is a great deal of satisfaction building the thing, you learn a lot and it's a great feeling when the thing works and works well.

If you can get the parts at whatever is an acceptable cost to you, are willing to take your time, put safety above all else then I say go for it.   Don't rush...I guess I spent most of a summer getting parts and building my tool chest amp. 

73
Roger, N4HZ

 
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AB5NI
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Posts: 31




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« Reply #12 on: February 06, 2019, 10:08:07 PM »

I've noticed, over the years, that the best homebrew gear I've even seen comes from people that take their time. It's like they make building something an adventure and learning experience, all wrapped into one. A good friend of mine and my electronics mentor -- as well as an avid builder -- Marty, WB0ESV, told me to always take my time. "Set aside an hour or two a day for your project. Don't rush yourself and think things through. Keep at it, and before you know it, it will be completed and ready for testing." He said that was the ticket to success when building.

73,

Randy AB5NI
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I eat spaghetti code out of a bit bucket while sitting at a hash table, and I pay for the meal with cache!
W1ITT
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« Reply #13 on: February 08, 2019, 08:22:02 AM »

Of course, the answer to your question is.. "It depends."  I have built a number of full legal limit amplifiers over the years and am now in the process of finalizing a GS-35B build.  As a ham of over 52 years, I have collected a few parts, so tallying the "total" cost would involve going back a ways.  Although I have a fairly suitable Peter W Dahl plate transformer, I'm winding my own, on C-Cores to get exactly what I want, and that's costing a bunch more money.
I used to judge a hamfest/flea market based on whether or not one could build a full legal limit amplifier with all the major parts purchased (or at least available) on that day.  It used to be easy, but less so now.  Real good high power goodies seem to be less common these days.  That stash that G3RZB mentioned would make life easy for you.  Many of the parts that I have used were bought or traded or given by friends.  It's a nice feeling to have those tokens of cooperation in my rig.  The other thing to take into consideration is resale value of a homebrew amplifier.  Personally I don't give a hoot as I build for my own pleasure, but a commercial name-brand unit will retain  considerably more value than the parts that go into a homebrew rig.  Most hams, me included, wouldn't be interested in someone else's project, except perhaps as a parts supply.
I take a lot of satisfaction from getting on the air with a rig of my own design.  To me, though not to all, that's what ham radio is all about.  I'm not in the game to make a profit, just to have fun, and my time is probably not worth much more than 28 cents per hour..  This GS35B will probably be my last tube rig (or maybe my next-to-last...)  Solid state is rapidly becoming cost competitive, and the voltages are not as scary.
I am of the opinion that "real hams" build lots of stuff.  And I accept that not everyone is in that boat. If you want to build an amplifier just to save money, you may be barking up the wrong tree.  If the idea of putting your own handiwork on the air stirs your interest, and you have some ability as a metal basher and troubleshooter it will be a fine adventure.
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KX4QP
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« Reply #14 on: February 10, 2019, 03:03:22 PM »

I've heard that it is hard to find a suitable high voltage transformer for a tube amplifier in the UK, so  you may want to investigate that first.

Fortunately, HV DC can be sourced without a transformer in sight, using a Cockcroft-Walton cascade.  Basically a full-wave rectifier (can be either tube or solid state, though I don't recall seeing one that used tubes) that charges a capacitor with its DC output -- and then chain a number of them together in series.  If you're starting with 240VAC, each stage will give close to 350VDC, so three stages will get you 1000V.  Get the voltage high enough to regulate to what you want (and here, you might be ahead with a regulator tube, as a single part will regulate a voltage suited for a high power tube stage).  For your low voltages, you only need standard, easily sourced bits.

It's very highly recommended that your rectifiers and capacitors be rated for at least twice your stage voltage, and if you're going above 1000VDC, you may find it helpful to either pot the entire (solid state) unit in wax, or put it in a jar full of mineral oil to provide additional dielectric strength compared to air.
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