After nearly 10 months of planning and work, I am able to make my first transmissions on LF! I am running 10 watts from the transmitter. EIRP is a bit less than the claimed 0.1 watt. I am having some
Hi Paul, Congrats to your first transmission! How do you couple the PA output to the antenna? Are you using an isolating ferrite transformer? Without knowing your problem in detail, this is the first
Paul, I had to wait a bit until the fading gods relaxed a bit, but was able to copy your N1BUG CW ID just before 2332Z. Copy was easy through a 30 Hz audio filter. K3RWR's carrier is is also plainly
Hi Stefan, Thanks! This has been a very exciting journey for me. I'm trying not to be too discouraged by early problems. I do use an isolating ferrite transformer at the antenna. It is very similar t
Hi Paul, Am 21.12.2017 00:47, schrieb N1BUG: I'm trying not to be too discouraged by early problems. Wouldn't it be almost boring without early problems? I do use an isolating ferrite transformer at
Hi Stefan, What ever the design is, i would use an isolating transformer. BTW how do you match the antenna feed point impedance to 50 Ohm then? Do I need two transformers? What I use now is three sta
Hi Paul, I'm not in your shack, so i can only guess where the problem is coming from... The function of the transformer is not only to match the impedance, it is also for decoupling the shack earth f
Hi Stefan, The C on the gate is not a good idea i think. Better try a 10...22 Ohm resitor or a ferrite bead in front of the gate. I removed the C on the gate and added a 15 ohm resistor in front of t
Hi Paul, So at least there is an improvement. Does the blue core become warm during operation? How does the drain-voltage look like? 73, Stefan Am 23.12.2017 14:13, schrieb N1BUG: Hi Stefan, The C on
Hi Stefan, Does the blue core become warm during operation? No, it stays completely cold. Same for the two cores in the LPF. How does the drain-voltage look like? It is hard to describe and so far I
It will run perfectly stable into the 50 ohm dummy load at 25 watts output. Into the antenna it will do no better than 17 watts, usually less before something goes wrong. This looks suspiciously like
This looks suspiciously like there is still some reactance in the antenna system Paul. If it's anything these amplifier types can't tolerate it is reactance in the output. It does seem that way Steve
Hi Paul, Am 23.12.2017 23:36, schrieb N1BUG: For anyone trying to follow along, this is my current version: http://n1bug.com/ASB_LF_Amp-20171223.jpg The circuit looks good to me now. Maybe it helps t
Are you sure your 50uH choke is doing its job? 9t to get 50uH suggests ferrite witout a gap. IN which case FDC thought the winding will be saturating the ferrite, driving it into non linearity an
No. I'm not sure of anything! I'm a HF/VHF/UHF and tube amplifier guy who decided to get on LF. Working with FETs and ferrite is all new to me. 9t to get 50uH suggests ferrite witout a gap. IN which
Hi Paul, Stefan my first PA for MF and LF, based on a IRF520, was similar. However, I used a most appropriate 1:4 output transformer instead a 1:9. With 13.8V, a 50mA bias current is more than adequ
The other thing about that circuit that is wrong is the power out specification for the turns ratio / loading resistance. For a single ended PA, Pout max = Vdd ^2 / 2 / RL. With a 9:1 (3:1 turns) t
Hi Andy, This is very interesting, because 12 watts is what I think I have consistently been able to generate into the antenna before problems creep in. I can easily accept that this amplifier may on
The scopematch circuit looks reasonable. Arithmetic is correct (as an aside, I always group constants together for calibrations like that. Measuring peak to peak across a 50R load, power then be
Hi Andy, Thank you very much for that. I am learning and knowledge sometimes comes together from bits and pieces in discussions like this. Anything is possible with this amp or the filter. I tried wi
