Thought I'd try one of these.....

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Re: Thought I'd try one of these.....

Post by shuffy » Sun Sep 27, 2015 1:42 pm

thewoodstarr wrote:With our own exciter, which can deliverer 15 Watts, but set @ 1 Watt. And on a switch mode @ 27 Volts... 120 Watts, but that is it, there is no more...... Next Question?
So 110W out for 300mW in, and 120W out for 1000mW in.

No more questions, your honour.

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Re: Thought I'd try one of these.....

Post by Analyser » Sun Sep 27, 2015 8:46 pm

Some of these threads really make me chuckle.

"thewoodstarr" writes like a mad person, both in electronic terms but also his general ranting.

Firstly, it is (very) unlikely that you will get 110w output with 300mW drive with a device optimised for the UHF band and running at 27v. Shuffy politely alluded to this already which is why I kept my trap shut.

Secondly, you can't measure harmonics using an analogue oscilloscope. :geek:

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Re: Thought I'd try one of these.....

Post by radio-berlin » Sun Sep 27, 2015 8:58 pm

If your amp is reading 110watts at 300mw drive then i strongly suggest you put it on an analyser as it sound to me your meter is reading harmonics and self oscillations combined with your main output carrier. You will never get 110w from 300mw drive at 27v, there must be something wrong. If you need help just ask

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Re: Thought I'd try one of these.....

Post by pjeva » Mon Sep 28, 2015 4:11 pm

It probably self oscillates, and gives false reading on power meter. Think like this, if you need like 4 watts with expensive FET to get 600W output with 50V supply, is it possible to get 1/6 of that power with 1/13 input power and half of supply voltage and low-cost FET?
Push pull designs have lower intensity of harmonics, but with self oscillations in gate circuit they have no problem. You could try to strap self oscillations with C / R combination from gate to ground and check power then...

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Re: Thought I'd try one of these.....

Post by Shedbuilt » Tue Sep 29, 2015 10:59 am

pjeva wrote:It probably self oscillates, and gives false reading on power meter. Think like this, if you need like 4 watts with expensive FET to get 600W output with 50V supply, is it possible to get 1/6 of that power with 1/13 input power and half of supply voltage and low-cost FET?
Push pull designs have lower intensity of harmonics, but with self oscillations in gate circuit they have no problem. You could try to strap self oscillations with C / R combination from gate to ground and check power then...
Or a clue (to self-oscillation) can sometimes be seen, by removing drive - either by powering down the driver board, or by manually activating the OLPD (if fitted).

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Re: Thought I'd try one of these.....

Post by Shedbuilt » Tue Sep 29, 2015 11:06 am

Analyser wrote:
Secondly, you can't measure harmonics using an analogue oscilloscope. :geek:
Not unless it's a very special oscilloscope..... One of a kind..... Almost......

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Re: Thought I'd try one of these.....

Post by Shedbuilt » Tue Sep 29, 2015 12:06 pm

thewoodstarr wrote: Hi,
Not being funny, as most are on this forum, but you have posted a low pass filter for a 2n4427 Transistor
Actually, no. Stephen Moss's write up, which I included in my post, clearly describes the design limitations. He suggested up to 25W as shown, up to 45W with parallel caps, and describes how to make it suitable for higher powers. I haven't used that exact design as published, but definitely very similar. I usually "do the math" - then fine tune, but I trust the source, and would be surprised if it doesn't do what it says on the tin.
I posted it primarily to illustrate the inductor dimensions, capacitance values, and to demonstrate that the inductors for a filter, to roll off just above Band II, could probably be fitted into the space occupied by the inductors of the existing LPF (as supplied with the MRF 186 board). Parallels of high voltage ceramic discs, to make up the same capacitance values would be ok. ATC 100b series, or metal clad mica would be better.
If it really is -60dB or better - especially at 2F, then it's doing well, and I think the 2F suppression must be helped a lot by the push-pull symmetry. If it becomes asymmetric, I think that will go out of the window, so a lower LPF cutoff frequency would give a better comfort factor.....

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Re: Thought I'd try one of these.....

Post by thewoodstarr » Sun Oct 04, 2015 1:26 am

builtinashed wrote:
thewoodstarr wrote: Hi,
Not being funny, as most are on this forum, but you have posted a low pass filter for a 2n4427 Transistor
Actually, no. Stephen Moss's write up, which I included in my post, clearly describes the design limitations. He suggested up to 25W as shown, up to 45W with parallel caps, and describes how to make it suitable for higher powers. I haven't used that exact design as published, but definitely very similar. I usually "do the math" - then fine tune, but I trust the source, and would be surprised if it doesn't do what it says on the tin.
I posted it primarily to illustrate the inductor dimensions, capacitance values, and to demonstrate that the inductors for a filter, to roll off just above Band II, could probably be fitted into the space occupied by the inductors of the existing LPF (as supplied with the MRF 186 board). Parallels of high voltage ceramic discs, to make up the same capacitance values would be ok. ATC 100b series, or metal clad mica would be better.
If it really is -60dB or better - especially at 2F, then it's doing well, and I think the 2F suppression must be helped a lot by the push-pull symmetry. If it becomes asymmetric, I think that will go out of the window, so a lower LPF cutoff frequency would give a better comfort factor.....
I can see where you're coming from, but trust me it works fine as it is, these push pull devices are far better than the devices we used to use just 10 years ago, although I am still a fan of the BLF177, fantastic! But getting back to this device I think the Caps are fine on the output, you would need to change them for above 100 Watt, but if it's not broke don't fix it. One thing, I have only tested this into a Dummy Load, I don't know what the result will be up a a dipole? That could be a different result altogether! As you know the bench test doesn't mean it works in the real world. I need to sell this, as I have made a a tidy Rig out of it, so I had better find out! I will let you know! Cheers....

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Re: Thought I'd try one of these.....

Post by RF-Head » Sun Oct 04, 2015 8:48 am

I have seen a few old rigs from tecknicks and tested on my spec and giving a clean output
Not tested a woody box,but i say you post a picture and we can see what quality you built :smoke

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Re: Thought I'd try one of these.....

Post by Analyser » Sun Oct 04, 2015 10:52 am

teckniqs wrote:Maybe check it on an analyser then? Are you that guy they call 'Woody' who doesn't put any filtering in his rigs?

....That makes sense.
Unfortunately, this is correct. I've never seen a W***y rig but I was asked to repair a B1 link box of his a couple of years ago, and it was about the worst thing I've ever seen. It was supposed to be 20w and it was doing about 2w on B1 and 14w in the aircraft band. Matching was roughly tuned for B2 and no output filtering.
Alongside that the PLL was conpletely unstable and the audio coupled in to the oscillator with a 10nF capacitor. I couldn't work out at the time if that was done on purpose to try and stabilise the PLL but in the end I decided that would be far too clever of the builder. It was just like someone soldered random components into a box. Plus I got a shock off it because the mains live was brought to the front of the case and switched using one of those tiny Maplins micro toggle switches. The station who brought it to me paid a lot for it (I'd rather not say how much) and were told it was the best out there.

Mr "woodstarr", I'm not intending to slag you off for fun (you might be a really nice fella) but the equipment I saw was really really bad, you've still got a lot to learn about electronics and RF and letting stuff like that out of your workshop is not doing the scene any good. You might be selling 100s of rigs to big name stations but that doesn't make the equipment good. You have to remember that stations just put these things up on an aerial and have no test equipment to check them. If you keep on making stuff that broadcasts in the aircraft band you're going to end up in jail pretty quick.

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Re: Thought I'd try one of these.....

Post by RF-Head » Sun Oct 04, 2015 12:04 pm

@wisepranker
Did you had a woody box? i remember a picture you send me of a 150 and 300W box ?
You know the one with lots of tin :)

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Re: Thought I'd try one of these.....

Post by shuffy » Sun Oct 04, 2015 3:40 pm

teckniqs wrote:no one cares if Flex and Fresh Sounds use your junk. ;)
Flex don't use "woody" boxes.

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Re: Thought I'd try one of these.....

Post by thewisepranker » Sun Oct 04, 2015 3:58 pm

RF-Head wrote:@wisepranker
Did you had a woody box? i remember a picture you send me of a 150 and 300W box ?
You know the one with lots of tin :)
:lol:

It may well have had parts from a Woody box in it - that 150 W rig was made up of recycled bits of old everything, including what looked like cut up bits of clear plastic from an A4 document wallet.

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Re: Thought I'd try one of these.....

Post by RF-Head » Sun Oct 04, 2015 5:58 pm

@wise
Yes i remember and was looking for the picture but can't find it anymore :(
Flex use other boxes and i know

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Re: Thought I'd try one of these.....

Post by thewisepranker » Sun Oct 04, 2015 6:49 pm

Don't Flex use whatever is down some else's shaft?

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Re: Thought I'd try one of these.....

Post by Analyser » Sun Oct 04, 2015 7:57 pm

thewisepranker wrote:Don't Flex use whatever is down some else's shaft?
Yes.

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Re: Thought I'd try one of these.....

Post by Renegade Moods » Sun Oct 04, 2015 9:06 pm

RF-Head wrote:I have seen a few old rigs from tecknicks and tested on my spec and giving a clean output
Not tested a woody box,but i say you post a picture and we can see what quality you built :smoke
:lol: :tup

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Re: Thought I'd try one of these.....

Post by thewoodstarr » Thu Oct 08, 2015 8:39 pm

Oh this is classic the way this thread has turned about? Its laughable! Getting back to the original post. For £25.00 this little chinese Amp is great! Its is unlikely to cause any problems, so if you're on a budget, and have the skill to build it, its a good buy!

Again the board was tested @ 27 Volts.
From a 1 watt drive it produced just under 120 Watts @ 98 Mhz.

The only problem I found was that it self Osculated when no drive was applied.

This is an easy fix, but everyone on here is professional, therefore you will know how. :lol:

Laters! :lol:

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Re: Thought I'd try one of these.....

Post by RF-Head » Thu Oct 08, 2015 9:14 pm

Again the board was tested @ 27 Volts.
From a 1 watt drive it produced just under 120 Watts @ 98 Mhz.

The only problem I found was that it self Osculated when no drive was applied
Lol time for a spectrum analyser then
110W with 300mW input now we know how :whistle :whistle :whistle

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Re: Thought I'd try one of these.....

Post by thewoodstarr » Thu Oct 08, 2015 11:56 pm

Analyser wrote:
teckniqs wrote:Maybe check it on an analyser then? Are you that guy they call 'Woody' who doesn't put any filtering in his rigs?

....That makes sense.
Unfortunately, this is correct. I've never seen a W***y rig but I was asked to repair a B1 link box of his a couple of years ago, and it was about the worst thing I've ever seen. It was supposed to be 20w and it was doing about 2w on B1 and 14w in the aircraft band. Matching was roughly tuned for B2 and no output filtering.
Alongside that the PLL was conpletely unstable and the audio coupled in to the oscillator with a 10nF capacitor. I couldn't work out at the time if that was done on purpose to try and stabilise the PLL but in the end I decided that would be far too clever of the builder. It was just like someone soldered random components into a box. Plus I got a shock off it because the mains live was brought to the front of the case and switched using one of those tiny Maplins micro toggle switches. The station who brought it to me paid a lot for it (I'd rather not say how much) and were told it was the best out there.

Mr "woodstarr", I'm not intending to slag you off for fun (you might be a really nice fella) but the equipment I saw was really really bad, you've still got a lot to learn about electronics and RF and letting stuff like that out of your workshop is not doing the scene any good. You might be selling 100s of rigs to big name stations but that doesn't make the equipment good. You have to remember that stations just put these things up on an aerial and have no test equipment to check them. If you keep on making stuff that broadcasts in the aircraft band you're going to end up in jail pretty quick.[/quo


Ok well wasn't one of mine, I did not make band one equipment. Always Microwave. You said the audio was coupled to the Oscillator with a 10nF? Hmm I am sure your a very nice guy, but how would that work full stop? So this device never worked? Do you mean 10 uF? Look it was nothing to do with me me, I never made band one equipment?

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