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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Ten Tec Model 405 Help

Reviews Summary for Ten Tec Model 405
Ten Tec Model 405 Reviews: 4 Average rating: 4.8/5 MSRP: $149
Description: HF Amplifier rated at 50 watts out with 1-3 watts drive. Originally sold
as an accessory to the Argonaut QRP rig
Product is not in production.
More info: http://
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W5WAA Rating: 5/5 Nov 7, 2016 06:35 Send this review to a friend
Works well with Flex 1500  Time owned: 6 to 12 months
I just recently got one off eBay for less than $200. This is my second one, sold the first one after I found myself working 5 watts most of the time and not needing it. Recently found myself needing a few more watts and got another one.
Works like a charm. I usually use only 25 watts on the 1500 when communications is poor, I have used it up to the full 50 watts on occasion. Only "problem" is the protection circuits that act to stop you from blowing out the output transistors, they'll tolerate up to 3:1 SWR, go much above this and it will blow the units 10 amp fuse. I also put a slow-blow 5 amp fuse in series with the 12v power supply, which is easier to change if I need to. As long as you keep the SWR down you'll be fine, they have been around about 40 years.
HFHAM2 Rating: 5/5 Feb 26, 2016 20:05 Send this review to a friend
Still works great  Time owned: 0 to 3 months
I recently acquired a Model 405 linear amplifier in mint condition and use it with my Ten Tec Argonaut VI (Model 539) when conditions warrant it. They were originally sold as a companion to the Argonaut 509 transceivers back in the 1970s.

With 1-3 watts of input, it'll easily put out 50 watts on all bands including the WARC bands; even though they are not listed on the band switch (which controls the low pass filtering). T/R switching is by RF sensing so no relays, special cables or manual T/R switching is required and it has a fully variable T/R delay from instant up to several seconds which you can adjust to stop it dropping out of transmit mode e.g. between words. Bypass is controlled by a push-button power switch. All controls are front-panel mounted and there are also lighted meters for RF Watts out and SWR.

Needs 12-14 VDC at 8 amps. It has a funky "4 pin Jones" power plug, so make sure you get that with it or use a matching power supply (e.g. the Ten Tec Model 250). I think you can still find the Jones plugs if you search a little though.

Although this thing's upwards of 40 years old, it still looks and works like new. A real bargain compared to Ten Tec's latest (expensive) 100 watt linear and as it's a Ten Tec, you know it was built to last and meets the FCC regulations (which may not be true of that home-brew or "made in China" eBay find).
WB4TJH Rating: 5/5 Nov 10, 2012 07:36 Send this review to a friend
Solid old qrp amp.  Time owned: more than 12 months
I bught one of these new back in the 1970s along with an Argonaut 509 and it worked well. But like an idiot, I sold it. But last year, I bought another mint one from a friend for $200. The 405 sits alongside my Elecraft K2, and it works flawlessly. What I really like is the fact it needs no relay hookup--it uses RF sensing and when I speak into the mike, it comes on. The delay is fully adjustable from the front panel and it makes it very easy to connect to any QRP radio out there. I get 50 to 65 watts out and the 405 never misses a beat. I also have a Ten Tec Hercules II amp in the shack, and together, they both do a superb job. If you can find a mint 405, pick it up. It's a no brainer amp and the going price is around $200 or so. TenTec has a new 100 watt QRP amp out now, but it costs upward of $800, so that makes the old and rare 405 a bargain, if you can find one.
AB7KT Rating: 4/5 Jul 8, 2011 09:51 Send this review to a friend
Nice QRP Accessory  Time owned: more than 12 months
There seems to be a moderate amount of interest in the QRP community for a small amp to enhance the performance of a QRP rig when conditions are rough. I bought my Ten Tec Model 405 amp used several years ago and for some reason stuck it away in a box and never did anything with it. Recently I "found" it and finally hooked it up. After all these years it seems to work fine. I am driving it with a Yeasu FT-817 with one watt. The power output of the amp varies with the band. On some bands it delivers close to the rated 50 watts, on other bands the power output is as low as 30 watts. I made several QSOs using this amp and again, it seems to work fine.
I am happy I bought it and recommend it if the price is right.

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