eHam

eHam Forums => HomeBrew => Topic started by: MM0IMC on February 04, 2019, 06:11:52 AM



Title: Cost of Building an HF Amplifier?
Post by: MM0IMC 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?


Title: RE: Cost of Building an HF Amplifier?
Post by: KU3X 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


Title: RE: Cost of Building an HF Amplifier?
Post by: KS2G 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?



Title: RE: Cost of Building an HF Amplifier?
Post by: AB5NI 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 :D.

73,

Randy AB5NI


Title: RE: Cost of Building an HF Amplifier?
Post by: W1VT 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.


Title: RE: Cost of Building an HF Amplifier?
Post by: KD7RDZI2 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.


Title: RE: Cost of Building an HF Amplifier?
Post by: N8CBX 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


Title: RE: Cost of Building an HF Amplifier?
Post by: N8CBX 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


Title: RE: Cost of Building an HF Amplifier?
Post by: W1VT 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.


Title: RE: Cost of Building an HF Amplifier?
Post by: N8CBX 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


Title: RE: Cost of Building an HF Amplifier?
Post by: G3RZP 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.


Title: RE: Cost of Building an HF Amplifier?
Post by: N4HZ 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

 


Title: RE: Cost of Building an HF Amplifier?
Post by: AB5NI 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


Title: RE: Cost of Building an HF Amplifier?
Post by: W1ITT 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.


Title: RE: Cost of Building an HF Amplifier?
Post by: KX4QP 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.


Title: RE: Cost of Building an HF Amplifier?
Post by: G3RZP on February 11, 2019, 04:45:18 AM
You can often get given parts. We (G4FNC and myself) got two vacuum variables as wedding gifts.......


Title: RE: Cost of Building an HF Amplifier?
Post by: LA9XNA on February 11, 2019, 02:07:22 PM
You can look for a "Donor amp" and use that as a starting point.
This will give you many of the components required to get started.
The most important is probably the voltage and amps on the HV transformer to fit with the tubes you plan to use.


Title: RE: Cost of Building an HF Amplifier?
Post by: W1VT on February 11, 2019, 04:08:43 PM
Cockcroft-Walton cascade may not be suitable for typical SSB operation with its high peak to average ratio.  Similarly, the pure tone of traditional CW may be hard to achieve with a cascade.


Title: RE: Cost of Building an HF Amplifier?
Post by: MM0IMC on February 12, 2019, 04:11:55 AM
It's difficult to know where to start, as I've a fair collection of Russian NOS valves to choose from.  ::) I've got a GS35B, a couple of GS31B's, a couple GI7B's and a GI46B.

I've been advised in the past to stay away from microwave oven transformers. I do have ten Chinese 450V, 220 microFarad electrolytic caps I could use. I've also got a separate transformer that would be good for use as a heater transformer and would easily accommodate the largest Russian valve.


Title: RE: Cost of Building an HF Amplifier?
Post by: PU2OZT on February 12, 2019, 05:35:36 AM
CW cascade may not be suitable for... CW...

That was a good one I sure remember when taking my Extra
 ;D ;D
Oliver


Title: RE: Cost of Building an HF Amplifier?
Post by: N8FVJ on February 13, 2019, 06:20:55 AM
I suspect some used amplifiers would be cheaper than the cost of building a new amplifier.


Title: RE: Cost of Building an HF Amplifier?
Post by: WA5VGO on February 13, 2019, 07:22:55 AM
It’s not all about cost. It’s also about pride and the learning experience.

Darrell


Title: RE: Cost of Building an HF Amplifier?
Post by: K3UIM on February 13, 2019, 09:51:40 PM
Amen, Darrel, although I'm thinking not too many of todays hams are doing very much building. (Mores the pity!)
Seems that back in the 50's and 60's we didn't have the necessary bucks to do a lot of buying so learned to enjoy the thrill of building and learning.
(Judas Priest! I'm aging as I type!!) Hi.
Charlie, K3UIM


Title: RE: Cost of Building an HF Amplifier?
Post by: N3DT on February 21, 2019, 06:39:48 PM
Building a good amp from scratch would be a huge project and fraught with lots of learning. If you want to do it, go for it, but be prepared to spend more than you would for a new one and lots more time than you expect. I've thought about it, but just couldn't, I bought a perfectly good 80B for $900 and found other stuff to do. I'm not sure learning how to build an amp is useful at this point in time, other than for the satisfaction and bragging rights. I've seen some really nice homemade stuff though. It's not for everyone.


Title: RE: Cost of Building an HF Amplifier?
Post by: WA5VGO on February 22, 2019, 07:42:16 AM
Building and experimenting is the essence of the hobby. How can anyone find satisfaction passing a test that 10 year old kids can pass and then operating a bunch of store bought appliances? How can someone with an extra class license justify purchasing a manufactured dipole or paying someone to install a microphone connector?

If the only objective of the hobby is simply to communicate, just purchase a computer or cell phone. With almost any hobby, the objective should be to continuously push your skills and knowledge.

Darrell


Title: RE: Cost of Building an HF Amplifier?
Post by: MM0IMC on February 23, 2019, 10:32:57 AM
Building and experimenting is the essence of the hobby. How can anyone find satisfaction passing a test that 10 year old kids can pass and then operating a bunch of store bought appliances? How can someone with an extra class license justify purchasing a manufactured dipole or paying someone to install a microphone connector?

If the only objective of the hobby is simply to communicate, just purchase a computer or cell phone. With almost any hobby, the objective should be to continuously push your skills and knowledge.

Darrell

I don't consider myself to be a dope with a soldering iron, having built a few things myself, having repaired my former Ameritron AL-811H and done countless microphone plugs for others. ;)  It's just building an amplifier from scratch is a magnitude of difference to what I've done before and a far more expensive! :o


Title: RE: Cost of Building an HF Amplifier?
Post by: K6AER on February 24, 2019, 10:17:37 AM
You can obtain a lot of the parts from MFJ, Harbach, transformers from Tran-X in Colorado Springs.

For knowledge you might want to repair a few used amplifiers (Grounded Grid) until you see how and why tings are done is a certain way.

Many amplifier control assembles can be bought from various hams. Most material and boards being offered are for solid state designs.

You will never be able to build one for the cost of buying a well working used amplifier.

As others have  said the knowledge is priceless.



Title: RE: Cost of Building an HF Amplifier?
Post by: AA4PB on February 24, 2019, 10:44:04 AM
There are certainly advantages to building your own tube type amp such as knowledge gained, pride of good workmanship, etc. However, the new solid state amps offer many advantages such as:
1) No tuning required. Instant band change.
2) instant on.
3) Microprocessor monitored and controlled. The processor monitors voltage, current, heat sink temperature, power output, and SWR. If anything goes out of spec then the controller either reduces power or cuts off the amp in order to protect it from damage. The processor controls fan speed so noise is minimized by setting the fan speed only as high as needed to keep things cool.

I've built a few amps (home brew and kits) since my entry into ham radio in 1959. However, when deciding it was time to get another amp recently I decided that it made more sense "for me" to purchase a solid-state amp.



Title: RE: Cost of Building an HF Amplifier?
Post by: W1VT on February 24, 2019, 01:04:59 PM
But, those are valuable skills. You could expand on those skills to design a phased array that monitors the current in each element.  As well as other specialized functions that can't be affordably mass produced.


Title: RE: Cost of Building an HF Amplifier?
Post by: K8AXW on March 03, 2019, 11:43:27 AM
The pleasure of building an amp is one factor that should be factored in the "cost!"  As a builder of a few amps from 20w SS to 1500w hollow state, may I suggest:

1 - Pick a circuit you consider "buildable."  (Complexity, not one of a kind part, etc.)
2 - Create a list of parts required.  This part is half the fun of amp building.
3 - Start your search for the parts and keep a record of where and how much.
4 - Add it all up and if it falls within your price range start acquiring the parts, which includes  sources mention by several others here.
5 - Start the planning where everything goes so you don't start the  metal work only to find that there isn't room for the parts!
Don't hurry.  Building one of these things takes planning and work that you don't want to do over and over and this  is where the fun is.  Not the actual operation!  Have fund doing it!















Title: RE: Cost of Building an HF Amplifier?
Post by: KX4QP on March 04, 2019, 04:15:12 PM
One thing about "your price range" -- I built a telescope around twenty years ago.  I spent about the same money it would have cost to buy a similar instrument, but a) I never spent more than about $50 at one time, and b) I got an instrument that performed roughly as well as a slightly larger, much more expensive commercial scope.  Your "price range" can be much more flexible when you don't need all the money at once.