Check RD30HVF1

[Albert H]

It doesn't matter. Thicker tubing will be stronger (but heavier). Any tube thickness will be fine at 100W.

[Sietedj]

It doesn't matter. Thicker tubing will be stronger (but heavier). Any tube thickness will be fine at 100W.

OK, thanks!!!

[Sietedj]

This morning I went to test the new J-Pole antenna to finish adjusting the swr although they are in 1: 2 but I wanted to try to lower it even more if I could. The case is that in the second test I've done the transistor has been broken. I have done several tests inside my house without problems and this last one has been on the roof, so I do not understand that it has been able to happen, if it is also for the static electricity when touching the box of the transmitter.
I'm going to have to look for some anti-static gloves to manipulate the box as well.
The fact is that I removed the transistor and I put one of the first ones that broke, it was proven that it did not work. I have bypassed the smd of the flashing photo for a moment and raised the needle of the ammeter over 6A, the power returned, and the transistor goes back to work. Occasionally it does some power variation, lowers a pair of watts and goes up again. It's been a few hours working fine and I do not understand how the broken transistor might recover. Has something happened to anyone?
Happy Holidays!!!!

[Albert H]

Varying power isn't easy to achieve. As the power output changes, the output match will also change. The manufacturer of the FET will specify an optimum quiescent current and the gate bias voltage will be slowly turned up from zero with no RF drive applied until that current is set. Apply the drive and you'll get the maximum gain from the stage. If you have a 30W transmitter, there's no point in turning it down to 20W - the field strength will be slightly reduced but not enough to be noticed by the listeners. Just set it up for maximum gain and don't fiddle with it again!

[Sietedj]

Varying power isn't easy to achieve. As the power output changes, the output match will also change. The manufacturer of the FET will specify an optimum quiescent current and the gate bias voltage will be slowly turned up from zero with no RF drive applied until that current is set. Apply the drive and you'll get the maximum gain from the stage. If you have a 30W transmitter, there's no point in turning it down to 20W - the field strength will be slightly reduced but not enough to be noticed by the listeners. Just set it up for maximum gain and don't fiddle with it again!

Thanks Albert!!!

[RF-Head]

So you bypassed the coupling capacitor between the driver fet and RD30
thats the way to go
now you have put 10-12 volts on the gate and then when adjusting the bias pot you get a short on the output of the driver fet
I never had any problems with this type of modules and sold many of them

[Albert H]

I was surprised by just how good the Chinese BFG135 into the RD30HVF is. I found one of those "CZH" efforts in the junk box. I disconnected all the exciter part so that the was just the two-stage PA. Feeding in 25mW at 98MHz and 13.8V from a battery gave me just over 25W of very clean power. I can now see why RFHead uses that circuit for his 30W boards!

I'm not entirely convinced by their tuned line PCB tracks - recalculating them could be a good idea - but the efficiency is astonishing, given that the matches aren't exactly optimal (by my calculations).

This experiment suggests that a really low noise VCO into a buffer then this PA could yield a cheap 30W 12V rig. The usual two-chip synthesiser and a reasonable heatsink, and this looks like a very viable approach.

[Sietedj]

So you bypassed the coupling capacitor between the driver fet and RD30
thats the way to go
now you have put 10-12 volts on the gate and then when adjusting the bias pot you get a short on the output of the driver fet
I never had any problems with this type of modules and sold many of them

OK, RF-Head, I do not know where the problem is, it will be that the RD30 is very sensitive and breaks to the minimum. I will try to wear the anti-static bracelet every time I touch the box and do something with it. This time I just removed the antenna connector to put the SWR meter.
Otherwise it goes well, the sound is quite good.
A greeting!!!

[rigmo]

Hello, I did not last even a week transistor, it has broken again. This time been without touching anything. Anyone would think that might be?
https://www.dropbox.com/s/7pjj62slsx5th ... a.jpg?dl=0
In the picture, where it says power is really adjust to adjust the power or bias?
In http://www.hf-electronics.nl they said it was to adjust from 0 to 30W.

You need add static coil protection on output... Ware you buy this transmitter i wont buy one?

[Albert H]

Years ago, before I started using DC-shorted aerials, I had static issues with MRF150 PAs. The cure was to put a 10k resistor from the output to ground. Any static voltage on the coax was shunted and couldn't cause problems.

Incidentally, I know one gentleman who used to like to steal gear was given a colossal static shock from a downlead on top of a block in West London. He ended up in hospital! This was the same chap who thought it a good idea to push drawing pins into coax.... He blew up a number of people's rigs when he wasn't able to get at them to steal them. He met his match with one that I built with a pair of MRF150s that were under-run. That rig would continue to work into a direct short! The character with the drawing pins got some severe RF burns from that rig....

[David Crespo]

Hello, I am sietedj with a new account, I just wanted to say that I have been using the transmitter for several years without problems since I changed the antenna, that when there was a storm because it was not short-circuited to ground, it melted the transistor. Now with a J pole everything is perfect.
Greetings to all!

[SD-E1102]

Nice to see you again and welcome back.
If you are having problems accessing your old account and you need to get back on it we can help.

Drop me a PM.

//////ADMIN

[David Crespo]

Nice to see you again and welcome back.
If you are having problems accessing your old account and you need to get back on it we can help.

Drop me a PM.

//////ADMIN

It is already solved with the new account, thank you!

[Albert H]

Hello, I am sietedj with a new account, I just wanted to say that I have been using the transmitter for several years without problems since I changed the antenna, that when there was a storm because it was not short-circuited to ground, it melted the transistor. Now with a J pole everything is perfect.
Greetings to all!

Greetings to your too.

The J-pole is DC-shorted, so really helps to eliminate the static problems seen with simple dipoles (if they're not using a Pawsey stub).

[rigmo]

im interested, how to reach green RD30 project?

[rigmo]

Hi Analyser,
The transistor is on heat sink, a fan and the temperature was below 40 degrees.
Today it rained but it has not been an electrical storm, I had transmitters running storms and nothing ever happened to me. I use an antenna on the roof. The SWR is correct, it is 0.Now I have another transmitter 6W working perfectly with the antenna.
I understand that it may be by adjusting the bias, but I thought that this adjustment was to vary the power from 0 to 30W which is what I thought. I ask where I bought the transmitter to see they tell me.

Hi,
Do you have protection on antenna system for static electricity discharge ?

[Albert H]

You'll have more issues with the feeder than the antenna. I've seen J-poles made out of plumbing pipe handling 500W without issues.

[David Crespo]

Hi Analyser,
The transistor is on heat sink, a fan and the temperature was below 40 degrees.
Today it rained but it has not been an electrical storm, I had transmitters running storms and nothing ever happened to me. I use an antenna on the roof. The SWR is correct, it is 0.Now I have another transmitter 6W working perfectly with the antenna.
I understand that it may be by adjusting the bias, but I thought that this adjustment was to vary the power from 0 to 30W which is what I thought. I ask where I bought the transmitter to see they tell me.

Hi,
Do you have protection on antenna system for static electricity discharge ?

Hello, I bought the equipment here: https://www.hf-electronics.nl/ I don't know if they still will.
After changing the dipole antenna I had for a J pole I no longer had problems with electrical storms.