Random thoughts on linears

General discussion topics, anything goes within the bounds of the forum rules.
Sangoma
Posts: 290
Joined: Thu May 28, 2020 4:04 am
Location: Coventry
Contact:

Random thoughts on linears

Unread post by Sangoma »

Been thinking quite a bit about linears and using them in recent weeks.

I want a linear to cover 160-6

It's no use to me if it does not have a built in tuner (what's the point in doing it all manually with modern technology?
I gave that desire when parting with my first FT101

It must follow the radio when changing bands.

The tuner must have memories.

The linear must not take up half the desk.

The linear must be protected from the power spikes some rigs are prone to.

The linear must be able to run the legal limit all day (with a bit extra to compensate for my 200yds of feeder :) ) without getting too warm.

The linear ideally should have a separate power supply.

The linear must be able to survive an open or short circuit output.

The linear must give full output for 5W input

The linear must have at least two antenna outputs, remembered in the tuner memories.


I think the only one that comes close costs much more than I would ever spend on something I rarely use.
The FL-7000 comes very close, but it is OLD

External tuners are a long way behind the game.
I have two LDG 1000s, but they have no comms with the rig, and are a problem anyway trying to tune.
I have a BLA 350 that will give 600W and run at 450W all day (modified, not standard, they give less than 300W standard)
Thought I would try it with an LDG 1000 and the X5105, as it gives over 400W with 5W in.
There come the problem, the LDG will not tune at 5W, and if you reduce the rig power and try to tune with the amp operational
the amp trips out as the SWR goes over 3:1 during tuning.

I have built two large amps, both are still running after more than two years in temperatures of 30C plus, the first one was
nearly the same size as the FL-7000, but with no internal tuner, the second one was smaller, but neither had all the
features I would like

I still have two 1200W modules, one of each type I used, and thought I would use one, but then thought I don't need that
power capability, half of it would do fine, and the amp module would be smaller.

I'm tempted to build another one, with all the things I want as the target, not because I will us it much, if at all, but just because I want to.
G 3 E J S
Sangoma
Posts: 290
Joined: Thu May 28, 2020 4:04 am
Location: Coventry
Contact:

Re: Random thoughts on linears

Unread post by Sangoma »

Trying to fit everything into the size I want is challenging to say the least, maybe not possible.
linp4.jpg
The PSU is in the pile there as well, but in truth is not the thing that gets in the way, as the tuner and LPF can go above and below it.

The aluminium it is sitting on is the size I want it to be.

The heatsink goes right across the back, I can cool it with less heatsink and more air, but that is noisy.

I could use a smaller amp, but the LPF and tuner will both handle 1 1/2 kW, so it seems daft to used them with a half power amp (though 600w would be ideal for me)

The things that make space tight seem to be the individual small boards, PSU cut out protection, tandem match, SWR protection board, input protection board and band decoders, TX/RX realays and antenna switching and tune attenuators and control.

Answer would be to build a couple board to do all that the small ones do, but I don't know if I want to do that when I have the tried and tested ones already.
Or to make the tuner and LPF smaller, and stick with 600W, but it wouldn't save much space, as the relays would be the same.

The commercial all in one packages also have compromises, tuners with limited range, toroids that are just about big enough, relays that are only just big enough (and fail quite often it seems).

Maybe I should assemble the BLF578/188 (forgot which device I bought) and do some heat tests, and go from there, it may well be more efficient than the 2933s.


Keen to get going, but don't know in which direction :lol:
G 3 E J S
Post Reply