RF Amplifier kits - Page 1
Forum section: electronics / rf-microwave

author: veedub565
author_rank: Frequent Contributor
timestamp: June 08, 2022, 05:06:16 pm
content: Has anybody ever tried building one of these (or similar) RF Amplifier modules into a working amplifier for amateur radio use ?https://www.enigma-shop.com/component/hikashop/product/816-amateur-radio-2m-high-power-300w-amplifier-module#prettyPhotoIt seems all you need is a case, RF Connectors, 48v 600W PSU, cooling fan, and some relays and circuitry to provide Tx/Rx switching. I believe some sort of protection circuit and SWR monitoring would be advisable too.I already have a couple of old commercial amplifiers. They appear to be a quite modular design in rack mount cases, with a 48v PSU, RF connectors, massive heatsink and quad fans. The frequency of these isn't useful at all for amateur use. The RF module simply bolts to the heatsink though, so could in theory be replaced with one of these kits. All I'd then need is some Tx/Rx switching, SWR monitoring and protection circuitry.or I could just buy a 2nd hand, purpose built amateur radio amplifier. Something like the Microset SR200 would work well enough for me. And probably a lot smaller and quieter too.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 08, 2022, 05:23:06 pm
content: Try using the search. Here's one of mine with a small load. I built this to test some mods I made to an old current clamp to increase it's bandwidth. Nothing to do with ham or CB radio.https://www.eevblog.com/forum/projects/home-made-pa-and-load/msg635226/#msg635226I've built some low power amps from scratch for various projects but all are fairly low power. 10W or so and sub 50MHz.

author: veedub565
author_rank: Frequent Contributor
timestamp: June 08, 2022, 06:11:28 pm
content: oh yeah, didn't think to search firstSo, you haven't built one of these modules or similar into a workable amplifier for amateur radio use then.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 08, 2022, 07:22:13 pm
content: Quote from: veedub565 on June 08, 2022, 06:11:28 pm"Similar" in that it was a wideband kit designed for 300W for 10-150MHz into a 50 ohm load.Of course, I show no heat spreader in my heatsink design as I did not require a lot of power to test the changes to my clamp. While I have no interest in CB or ham radio, the load was still 50 ohms.Others here have build similar amps as well but that's my take on the word similar.

author: veedub565
author_rank: Frequent Contributor
timestamp: June 08, 2022, 07:49:18 pm
content: It's a nice project to be sure, and you clearly know about amplifier design. With the example in your link though you don't appear to need to worry about the sorts of things which would be needed in a amateur radio amplifier, unless I've missed it. TX/RX relay switching and protection circuits to name a couple. I mean the manufacturers say they tested it into a short and open load, so maybe the protection is built in.What I'm really looking for is someone who's built one of these modules (or a similar type module, it doesn't have to be an Enigma one). And built it up into a workable amateur radio amplifier. What has to be added to the basic module, any pitfalls, etc . So yes you have built a similar type module, it's the application that's perhaps more specificAnd although I did use the search function, I didn't see anything quite what I was looking for. Sometimes knowing what exactly to searchforis the problem.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 08, 2022, 08:35:32 pm
content: When I had a license, I had a separate receiver and transmitter. I used a separate long wire antenna for the receiver and the power levels were low. I had no TX/RX switch. Then again, I had to know Morse code...Anyway, easy enough to get a good used switch. If you want it for HF, even easier. I don't remember the kit I used having any protection. Not even thermal. You could easily over drive the front end and damage it.For what I was doing, I wanted to use it over a fairly wide frequency range but really didn't care about distortion. I never considered adding any kind of filtering. You may just want something for 2-meters and can tune the amp for that one area. Another option may be to find a kit that has everything with it. It looks like the company where I bought my kit is out of business but I'm sure there's others.

author: veedub565
author_rank: Frequent Contributor
timestamp: June 09, 2022, 06:42:53 am
content: I do have an old miltary HF set (TRP8255) which can be configured for separate TX and RX antenna's, and I think that's how the signals regiment used it. For me though it's more convenient to use one antenna and the built in switch. For 2m work I've not seen a rig with separate TX and RX connectors, I'm using an 80's era Yaesu. Morse code hasn't been a requirement for a good number of years in the UK, I don't think one even has to do a practical anymore.These modules in the link I posted look like a good building block for building a 2m band amplifier though. I don't really need one, I don't really need 300W. It just looked an interesting project to repurpose some old commercial amplifiers that I already have laying around.