distorted asian rsl/pirate

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Albert H
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Re: distorted asian rsl/pirate

Post by Albert H » Sat Jul 02, 2016 12:24 pm

Dai Pole wrote: I shall wait patiently...
Wait on,pal. Revealing the details could compromise a very useful source of information from the "other side".
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MiXiN
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Re: distorted asian rsl/pirate

Post by MiXiN » Sun Jul 03, 2016 1:33 am

Albert H wrote:Why on earth would you want to use a BSX60? It's only a gnat's under a Watt, 30V and not a lot of gain. You could get away with the much more common 2N3866.
Thanks for your input, Albert.

I was looking for a datasheet for the BSX60, but the one I found was a bit vague and didn't mention the output power, etc'. Lots of the other info' just goes over my head.

As I have a load of 2N3866 in the parts drawers I'll substitute it with one of those.

The application uses a 2N2219 driving a BSX60, which then drives a 2N3924 which drives a BLY89A final - all running off 13.8V.

Thanks for saving me a few quid mate!

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teckniqs
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Re: distorted asian rsl/pirate

Post by teckniqs » Sun Jul 03, 2016 10:51 am

The 2219 is another crap device.

Albert H
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Re: distorted asian rsl/pirate

Post by Albert H » Sun Jul 03, 2016 7:56 pm

That PA strip sounds like hard work! The 2219 is good for about half a Watt, but has very little gain at VHF.

The BSX60 is a 30V device (which is why I suggested the 2N3866) but if you're running the PA at 13.8V, a 2N4427 will be a better choice, with more gain at lower voltage.

I bet this PA strip has lots of trimmers in each stage too. You could get the same result with a single modern FET!
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MiXiN
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Re: distorted asian rsl/pirate

Post by MiXiN » Mon Jul 04, 2016 10:41 am

Albert H wrote:That PA strip sounds like hard work! The 2219 is good for about half a Watt, but has very little gain at VHF.

The BSX60 is a 30V device (which is why I suggested the 2N3866) but if you're running the PA at 13.8V, a 2N4427 will be a better choice, with more gain at lower voltage.

I bet this PA strip has lots of trimmers in each stage too. You could get the same result with a single modern FET!
You're correct, Albert!

It's one of those crude old Smartkit 15W VFO Transmitters from back in the late 80s or early 90s, in fact, the 1st ever thing I broadcasted back in the day - a real pain.

My mate is in the process of moving home and has handed me a load of old junk, and this was amongst it in addition to a Dawson and some old NRG stuff.

I'll post an image later per chance you've never seen one of these contraptions.

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Re: distorted asian rsl/pirate

Post by Albert H » Tue Jul 05, 2016 7:08 am

As I remember, it had an "at frequency" oscillator, an FET buffer stage, then several transistors to get the power up. It also lacked much in the way of an output filter. It suffered from the oscillator getting heated along the board from the later stages, so they would drift badly. Smart actually made a PLL add-on board for a while, that was incredibly complicated.

Just for fun, we had a little competition between a few engineering friends recently, to build the highest power Band II transmitter with the fewest components. There were points scored for supply voltage, cleanliness, stability, broadband performance and power output. It had to have take-off points for PLL connection and it had to fit into an aluminium box 5½" × 3½" × 1¾". The winning entry (not mine, by the way) used a pair of the 30Watt Mitsubishi FETs for the PA, giving 50 Watts, a dual FET oscillator, a dual transistor buffer and a multi-pole output filter. It tunes the entire band without adjustment (except for tuning voltage).

I've been experimenting with the dual FET oscillator because it behaves somewhat like Stephen's push-pull oscillator, can give a very pure output, and is widely tunable with just the control voltage. It uses an additional pair of varicaps for the modulation and has compensation to keep the voltage swing required for full deviation the same across the band. It's dimensioned for 1V5 p-p for 75kHz deviation. The circuit will be put on here when I'm fully happy with it.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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Re: distorted asian rsl/pirate

Post by Dai Pole » Tue Jul 05, 2016 5:58 pm

Albert H wrote:
Dai Pole wrote: I shall wait patiently...
Wait on,pal.
That's a no then! Just as I thought.

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Re: distorted asian rsl/pirate

Post by MiXiN » Wed Jul 06, 2016 2:13 am

Albert H wrote:As I remember, it had an "at frequency" oscillator, an FET buffer stage, then several transistors to get the power up. It also lacked much in the way of an output filter. It suffered from the oscillator getting heated along the board from the later stages, so they would drift badly. Smart actually made a PLL add-on board for a while, that was incredibly complicated.

Just for fun, we had a little competition between a few engineering friends recently, to build the highest power Band II transmitter with the fewest components. There were points scored for supply voltage, cleanliness, stability, broadband performance and power output. It had to have take-off points for PLL connection and it had to fit into an aluminium box 5½" × 3½" × 1¾". The winning entry (not mine, by the way) used a pair of the 30Watt Mitsubishi FETs for the PA, giving 50 Watts, a dual FET oscillator, a dual transistor buffer and a multi-pole output filter. It tunes the entire band without adjustment (except for tuning voltage).

I've been experimenting with the dual FET oscillator because it behaves somewhat like Stephen's push-pull oscillator, can give a very pure output, and is widely tunable with just the control voltage. It uses an additional pair of varicaps for the modulation and has compensation to keep the voltage swing required for full deviation the same across the band. It's dimensioned for 1V5 p-p for 75kHz deviation. The circuit will be put on here when I'm fully happy with it.
This Smartkit 15W VFO is without the FET, however, the 1st Oscillator Transistor does get pretty hot and the inductor & compression trimmer get real hot near the BLY89A final - so much so the coil can't be touched!

I'm guessing this is one of the oldest revisions as it doesn't look exactly like the "Smartkit 1o21" that I had back in the day which is pictured and mentioned on Google. I recall the inductor and standard trimmer reach severe temperatures on that as well.

I'll make a thread in the Anorak subforum tomorrow just so everyone can have a laugh.

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Re: distorted asian rsl/pirate

Post by Albert H » Sat Jul 09, 2016 10:46 am

Dai Pole wrote:Do you have any proof? I shall wait patiently...
Just take a look at the "Community" licence specifications in the offerings last week from OFCOM. They deliberately make it clear that religion will not be considered as a "community". This is, apparently, in an effort to appease the less tolerant members of our society. Rather than have competing religious stations, they've decided that they're just not going to have any more.

There is an interesting technical wriggle that could be allowed to increase the permitted output power. Because of "interference", the London FM community stations are going to be allowed 50 Watts per plane! That sounds like 100 Watts with two equal planar components to me! With a bit of intelligent aerial design and a good high site (there are no limitations in the location height), I could cover most of London with a cracking signal!

There's also interesting limitations on financial input - they're really trying to make these stations non-commercial (so probably non-viable) - just OFCOM trying again to "prove" that community broadcasting can't work!
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"Because it doesn't know the words!"
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Dai Pole
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Re: distorted asian rsl/pirate

Post by Dai Pole » Mon Jul 11, 2016 10:50 pm

Albert H wrote:Just take a look at the "Community" licence specifications in the offerings last week from OFCOM. They deliberately make it clear that religion will not be considered as a "community". This is, apparently, in an effort to appease the less tolerant members of our society. Rather than have competing religious stations, they've decided that they're just not going to have any more.
RSLs are not "community" licences Albert, neither are the commercial licences. The community licence specifications are probably deliberately "inclusive" - probably due to the "less tolerable members of society" you talk about preaching for secularism in public whilst following another philosophy in their own homes.

I'm sure if you wanted to set up an RSL for Matzo Cracker FM in Golders Green or Stanmore Hill, you'd have no problem whatsoever. Watch out though, they have there own dodgy pseudo police force they call the Shomrim in those parts - even ringfencing off areas with what they call an "eruv". You won't find anything like that in Tower Hamlets, despite the bullshit claims of "sharon law"!

What were we talking about here? Oh yeah, dem mooslims bro! Sounds like you're the one with "tolerance" issues.

Albert H
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Re: distorted asian rsl/pirate

Post by Albert H » Tue Jul 12, 2016 8:08 pm

Pal - I have no "tolerance" issues. The clowns trying to get "community of interest" licences for religious stations - NOT RSLs by the way - are the ones with the issues!

These are the ones who've threatened me, my family, my home and even my dog. The "religious" nutters making the threats tried to carry them out on my friend LB when he was over here, and so two of them won't taste clean air for at least nine years (sentenced to 20 years for attempted murder and aggravated assault).

If they come after me again, they'll regret it - for a short while.....

They're always being turned down for licences (even though they flood OFCOM with illiterate applications) and they don't seem to understand what "£600 non-refundable" means. They're demanding free licences, without application fees, and are (usually) unwilling to provide sponsors names for the "due diligence / right and proper" legal checks.

When they get refused, they go and put some wailing racket on in East London that causes so much interference that it's removed in hours. Fortunately, none of them has a clue about anything to do with radio engineering, so they never cause widespread mayhem.
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"Because it doesn't know the words!"
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bristolpirates
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Re: distorted asian rsl/pirate

Post by bristolpirates » Fri Jul 15, 2016 5:51 pm

Albert H wrote: There is an interesting technical wriggle that could be allowed to increase the permitted output power. Because of "interference", the London FM community stations are going to be allowed 50 Watts per plane! That sounds like 100 Watts with two equal planar components to me! With a bit of intelligent aerial design and a good high site (there are no limitations in the location height), I could cover most of London with a cracking signal!
I got word today of a document published by the Community Media Association. Nothing that interesting, but apparently, some of their members have been moaning about pirates etc....

The association had a meeting with Ofcom, and there was mention that while Ofcom's policy is not to be lenient to pirates, Ofcom will not license community stations on frequencies where pirates often operate as it's likely that the pirates will just continue to operate and cause interference.

BUT I'm sure there's been plenty of cases where the opposite has been true. Ofcom license a freq knowing full well a pirate uses it or an adjacent freq and then the community station has to increase power or complains or whatever.

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Re: distorted asian rsl/pirate

Post by Albert H » Sat Jul 16, 2016 3:02 am

Up in the North West of England a few years ago, the DTI licensed an RSL on the same frequency as a commercial station, separated by only 45 miles. The commercial flattened the RSL within a few hundred yards of its site!

The RSL operators negotiated with the DTI idiots and were told that they couldn't change frequency, but could raise the antenna and increase their transmitter power. The RSL borrowed a 300W amplifier module and power supply, and their 25Watt RSL rig made a nice driver! They raised their aerial by 25m and used an antenna with gain.....

The commercial station on the same frequency couldn't hear themselves on their studio monitoring receiver!

OFCOM (and the DTI Radio Division before them) have showed themselves to be incompetent. Their licence restrictions and financial restrictions for the new "Community" licences make them impossible to operate unless they're going to exploit lots of unpaid staff.
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"Because it doesn't know the words!"
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