Discussion in 'Amateur Radio Amplifiers' started by K0IZZ, Aug 26, 2020.
I run the yaesu ft-991a and now the la-1000-a and a mfj-989b I will have go sign up there
I have an LDG-600Pro tuner but discovered these little linears have such a good matching range, I eliminated the tuner. I have a Hustler 5BTV vertical. My worse SWR is on 40M, a bit over 3 but the amplifier has no difficulty at all. My FT100D straight though does not appreciate it though, lol!
I bet lol
Every time I swear that I'm not going to buy any more radio equipment, you post something that whets my itchy (credit card) trigger finger.
... sounds like a fun project...
The pi-net does have good matching range.
But calling an LA-1000 a "kW' amplifier is misleading. It was "marketed" as a 1 kW PEP input power amplifier, which on a good day with a tail wind can run about 500W PEP output power.
That's pushing the tubes (30W Pd each, so four have a total of 120W plate dissipation rating) way, way, way beyond their limits. However, it can happen if you don't mind pretty bad IMD.
Normally linear amplifiers are rated output power = 2x plate dissipation rating. If we followed that rule, the LA-1000 and similar amps would be rated 240W output power. And at that power level, they're actually remarkably "clean." At 2x that, not so clean.
The "sweep tubes" are remarkable in many ways and some can be used up to 50 MHz. But they're not intended to run with red glowing anodes and the glass used isn't the real high-temp glass used in "transmitting" tubes.
Still, handled with care and reasonably low duty cycles, they can last a very long time.
thanks for the info I will be trying to keep it 250-500 watts so should be good for a long time thanks again
I've just picked up a really nice Dentron GLA-1000B, love the sweep tubes, will buy a spare NOS set but otherwise all I'm going to do is change out the 30 year old HV power supply components
I measured the ripple of the old capacitors with a digital scope and 2 kV probe but the HV capacitors were in remarkably good condition.
I had to tweak the meter shunt to make the front panel meter HV reading match my Fluke 77 DVM though. The HV reading reading on the panel meter differed by more than 100 VDC.
HI all I got it running but it will not tune up on 20 meters not sure why HELP