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French Pirate Alt'F discusses his FM Transmitters

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13th Jan '99 : Visit Alt'F's site at http://www.compu.ch/dderbes/Altf/Index.htm ( In French !!)
08th April '99 : See Alt'F's comments on the Broadcast Warehouse DIGILOG Stereo Multiplexor kit


09th June '98

Date: Mon, 08 Jun 1998 19:33:16 +0200
Wrom: AFXISHJEXXIMQZUIVOTQNQEMSFDULHPQQWOYIYZUNNYCGPKYLEJG contact Web Surf if you really need it>
To: Web Surf <web_surf@SPAM-TRAPhotmail.com>
Subject: Re: Pirate Radio Bulletin Board

Hi Web Surf,

I did not post a comment in your bulletin board entry, large texts are clipped.

************************************************************************
* I've already sent comments (sorry it was under Alt'F / good_question@my_Advice.fun, an
inexisting e-mail. Pirate radio and * SWL is *NOT* loved by French authorities)
************************************************************************
I send you ALL my comments, remarks, and feel free to use all or parts of them.


First, here are my comments on the Veronica 1W PLL and a comparison (if it means someting) with
a Ramsey FM-25A, as you requested:


Web Surf a crit:

> Dear sir,
>
> Thank you for visiting http://members.tripod.com/~transmitters.
>
> I appreciate your comments.
>
> Would you like to make a more detailed bulletin board entry re the kits you built :
>
> Was it easy to build

=> Yes. I did appreciate the Veronica 1W PLL's large PCB, IC's holes exactly placed, pre-wounded coils, some caps were marked with red or white ink to avoid confusion.

==> R25A: Easy too

I also did appreciate the gap between connectors for Power and Led's, it was possible to use standard connectors to "plug" into. I've mounted the kit in a case, and all connectors (RF, audio, DC In, led's) are plugged. I can unmount the PCB for maintenance in less than 1 min, without the use of a soldering iron.


> Did they ship on time ?

=> Veronica Yes, and they also reply quickly and very honestly to some questions (exposed later in this document)

=> R25A: Correct for an overseas invoice.

> Did it have all parts when it came ?

=> Veronica, Nothing was damaged or missing
=> R25A: Nothing was damaged or missing

> Did you test to see if it meets published specs ?

=> No, i do not have the equipment, but my ears (and a high-grade tuner + reference Class A amp + tuner/direct switch, without stereo coder) told me that the audio quality of the Veronica was excellent (relative to the price and the announced 0.2% THD)

=> R25A: What a B#*L S@%T of sound ! ( Editor's comments : Please pardon the French !)

> Hum level ?

==> absolutly no hum, hiss and very low noise level. Ii use a standard 9~15DC 4amp lab. power supply. No RF filtering nor RF decoupling.

==> R25A: Hum, noise and hisses problems, depending of DC wires location and of the captain's age!!
(Editor's comments : What's the meaning of this french phrase ?)
>
>
> Transmit range ?

==> OK for the 900mW
==> R25A: This is (luckily) not a transmitter. Call it a "modulator" or whatever else you want...

> Documentation ?

==> The circuit design description is missing. More missing when you look at the plans, the VCO and modulator section seems very interesting. I'd like to obtain informations about.

==> R25A: The only good thing you buy, and a good example of very-near-lie advertising (It may be useful if you need ideas of how-to sell S#*T to someone)

> Would you recommend this to a friend ?

==> Veronica 1W PLL *YES*
==> R25A: *NO*

>
>
> Other equipment you have built ?

==> Veronica's Stereo coder (not very good audio quality as i've sent in my last bulletin board)
==> Broadcast warehouse's stereo coder (better, but shiped with false caps). 15Khz input low-pass filter and 53Khz output LPF is a good point.

==> Ramsey FM25A, rev. 1.4: RF and Audio: * BLEAACH *
==> Ramsey linear LPA-1 RF Amp * BLEAACH * (put 15V dc and it burns. !!)

About Veronica's specs:

I've pointed to Veronica the difference between the 0.2% thd announced in their web site and the 0.5% thd i've found in the kit's specs, and asked if there also was a difference with their compressor kits. They honestly announced me that their comp. had some distortion at low audio frequencies. I did appreciate. They dared to take the risk that a customer do not buy something (that's what i did. They missed a sale, not a satisfied customer).

Summary:

As i've pointed in my Alt'F posts to your bulletin board, the better way to use the Veronica PLL is to feed it with a *PRO* stereo coder, and you really realize that it is a very good unit, from an audiophile point-of-vue.

The transmitter is stable, clean and doesnt unlocks, even with "hard to broadcast" material, and "reasonable" over-modulation

Yes, the harmonics seems to be a little bit high, but a simple LPF for direct antenna feed is OK.
I use a professional 1~20W RF amp, extracted from a "real" transmitter.

You can use this PLL as a building block for a high quality radio station, even for classical music (and it is not the easiest music to broadcast). Simply do not use stereo coder kits nor comp/lim kits.

Ok, that's all, folks !

Sorry for my poor english, and long life to your site !

Alt'F

 


(Editor's note : In response to the public demand for more information after his first post, Alt'F was kind enough to send me a huge Word document describing his activities, his gear, his opinions on equipment. We publish below most of the semi-technical bits, as this is a technical forum)

Alt’F Radio – Jul-14-1998

About pirate/low-power FM transmitters and my station

Alt’F low power FM radio station

History

When i was 14, i’ve build a 3W VCO FM xmtr kit sold by  Pantec , an italian kit manufacturer. I’ve made a pirate radio covering my town (somewhere between France and Switzerland) with very few parts : a mini mixer, a mike, two turntables, a REVOX tape recorder and a recording walkman for outdoor use.

The sound was horrific, the frequency was not twice the same, but the enthusiasm and program originality made the success of this small pirate radio.

The station broadcasted two hours the Wednesday afternoon and four hours the Saturday afternoon under various names (Radio moi-je, Relax FM, Radio Assassine) The music was as alternative as possible, in comparison to other commercial stations (artists such as Laurie Anderson, Alien Sex Fiend, Birthday party, Einsturzende Neue Bauten, Killing joke, Soft Cell, Sex pistols…) The programs also included interviews of citizens about disturbing and  tabou  topics, pirate live recordings and various sound patchworks and deliria.

I stopped this station as soon as i learned from a friend working at the air-control center in the airport that i was disturbing some of their communications frequencies.

14 years later, my station started  accidentally  again when i was using a wireless CD to Tuner stereo adapter. It was a very short range (20 meters) stereo modulator, tunable from 106 to 108 Mhz, with a very good audio quality. As i wanted to enhance his range by trying differrent antenna configurations to cover all my house and garden, i enjoyed again broadcasting my favorite musics and wanted to really put it  on the air .

My first approach was to try to build a little RF amp for my modulator. I’ve tryed different circuits and had a recurrent problem : more frequency drift of the transmitter. I’ve decided to find some information on the Intenet about radio kits, and the first i’ve found was Ramsey.

When i saw they had a low-power PLL stereo transmitter, i thought i’ve found exactly what i was looking for. I’ve immediately ordered and build this item, plugged it in place of my old stereo modulator, and… it was terrific ! the sound was bad, the PLL unlocked when strong bass occured, it was noisy, and my scanner stopped on all harmonics the FM-25A generates…

After searching and comparing published specs, i decided to order and build a Veronica 1W PLL transmitter and a Veronica stereo coder. It was another world, but the stereo coder was not perfect… I’ve tried the broadcast warehouse’s stereo coder. I found it was better than veronica’s but something was wrong with the treble frequencies. After carefully checking, i’ve found two wrong caps in the pre-emphasis section. I changed these two caps and then it, was OK.

I thought i could not get a better sound without buying a professional transmitter, which was out of my goals.

One day i saw on the Internet a list of used material published by a broadcast equipement dealer. I’ve contacted him and he had two stereo coder boards as replacement parts for his customer’s transmitters in stock. I’ve bought one for $150, wired and plugged it to my Veronica PLL, and… it was the nirvana !

Transmitters

My opinion about Veronica 1W PLL kit and Ramsey FM-25A kit

Ramsey's FM-25A kit: Nice toy

Good :

Bad :

Comments :

The FM-25A is a funny kit, with well designed PCB and manual. This transmitter is not suitable for micropower nor pirate broadcasting : The audio quality is poor and noisy, the PLL unlocks too easily, and the RF output has too much harmonics to be used without causing interferences.

It’s worse if you use the LPA-1 power amplifier (another Ramsey’s kit) wich is a very wide band (100Khz~1Ghz) aperiodic 1W RF amplifier. This is the best way to be caught by the FCC or your communications authority, because you also amplify all the FM-25A harmonics ! ! !

Ramsey says  The FM-25A is definitively not a toy  I say that this is a funny toy, but absolutly not a  professional quality transmitter 

VERONICA'S 1W PLL KIT : It's another world!

Good :

Bad :

No description of the technical design in documentation.

Comments :

The Veronica 1W PLL kit becomes more than a kit when you’ve built it.

This unit is a serious and fully operating FM transmitter with a high level of audio and RF quality, fully suitable for high quality stereo operation. The word  professional  may apply to this unit.

You can set it up and use it for micropower and/or pirate radio, without any problem. It is stable, reliable and easy to maintain and adjust.

With spurii @ –40dB, i recommend a simple RF low pass filter for direct antenna feed to avoid any risk of interference and meet the standard harmonics and spurii levels of licensed stations.

Notice that output power is influenced by the temperature of the last two RF transistors. Cool'em better.

There is a "peak" of RF output power at a precise voltage (12.6V for mine) Use a well stabilized and adjustable DC source. Adjust it (when hot !), and it’s OK !

The LED’s status may be wired (i.e. placed in front of a case) without creating any interference/malfunction.

Modifications and other opinion: Please visit this link: http://www.geocities.com/Area51/Nebula/3736/veronica_1_watt_pll.review.txt

Characteristics :

Stereo coders

Here are the two stereo coder kits i’ve built and used, with the Veronica 1W PLL transmitter.

Veronica cristal stereo coder kit :

Sounds better than a BA1404, but not as good as Broadcast warehouse’s one. The treble frequencies are  agressive  and  mettalic  (ok,ok, it’s subjective …)

Please note that the Veronica stereo coder seems to have been designed to be used with Veronica limiters, which includes 15Khz Lpf. I did not used these limiters, so the comparison may be not valid.

RCA audio connectors on board.

 

Broadcast warehouse filtered stereo coder kit

This compact and stereo coder has great features for his price. 15Khz low pass filter, 53Khz output low pass filter, cristal controlled sub-carrier and pilot tone generator. High quality PCB.

The treble frequencies are softer and cleaner (probabily the filters).

Stereo image is a little bit strange : the sound seems to come from the extreme left and right, with a kind of  hole  in the center. (yes, i’ve checked all)

No audio connectors on board.

Both kits are well packaged. Only Broadcast Warehouse’s stereo coder came with two wrong caps (bad pre-emphasis).

 

Stereo coders kits - comments :

These two stereo coder kits have the same default : Noise. They are easy to assemble and needs no adjustments, except audio input level. You can’t ask much more for the price.

If you already have a compressor/limiter, use the Broadcast Warehouse’s filtered stereo coder, if you don’t have a compressor/limiter, try Veronica limiters kits and Veronica Cristal stereo coder. Otherwise…

 

…The Veronica 1W PLL and a real professional stereo coder :

This is where you *ear* and reveals the real quality and potential of this transmitter. Try to find a stereo coder board (broadcast equipment dealers have these boards for maintenance) I’ve paid no more than $150 for my board in Europe, and it’s really not expensive for the quality you’ll obtain.

 

Dynamics processors : compressors/limiters:

Why handling dynamics ?

The first answer is that you CAN’T over-modulate your transmitter. When you do, you use another station’s bandwidth, and your audio quality is decreased.

The second answer is to try to maintain the perceived loudness of your programs constant.

The third answer is to maintain the highest audio loudness

These three goals are not achieved with the same devices.

The first processing you have to apply to your audio program is clipping, to prevent ANY over-modulating peak. The clipper is a device that totally removes all signals over a fixed level. This process, when applied continuously generates a lot of distortion, so consider that when clipping is needed, it’s a kind of accident. You should adjust your modulation to avoid frequent clipping.

The second goal, maintaining the perceived loudness of your programs constant can be achieved by a compressor/limiter. To do so, it must adapt the attack and release time to the program. A fixed attack/relase time comp/lim is not suitable for this processing.

Any comp/lim can’t remove all peaks. This phenomenom is inherent to the time constants used by compressors/limiters. All transcients shorter than the attack time are not compressed nor limited. (The attack time is the time before the comp/lim begins to reduce gains) The use of a comp/lim do not replace a clipper !

The third goal, maintaining the highest audio loudness should not be a goal for a pirate or a microbroadcaster. The price of such audio processors are not affordable. At my opinion, there is also a  philosophical  point-of-vue : You’ll be always smaller and poorer than licensed stations, so try something else to be better than them. The loundness race has put the audiophile quality out-of-the-scene. Don’t forget that FM was developed especially to broadcast high-quality audio. Accept to be 1~2dB of audio level below others station, and leave this extra level free for dynamics that makes music living and natural.

You can achive the first and second goal with an interactive dynamics processor, such as Behringer’s composer.

Don’t play with comp/lim kits, leave your money in your pocket, and wait until you can buy a Behringer’s composer (around $200). If you dont want to pay for this, simply find a clipper circuit and adjust manually your level to avoid clipping. This will be the more natural and less expensive audio processing !

And remember : clipping is required

Behringer’s Composer dynamics processor :

What a great composer/limiter/clipper ! This unit uses program-dependant attack/release time and hard/soft knee limiting mode.

The Composer has a clipper, this is required in front of any transmitter. It removes all remaining peaks.

One of his greatest feature is also his price (around $200), and this is a real professional studio equipment.

Plug a composer between your mixing board and your transmitter, you won’t need any other audio processing unit. All kind of programs are well processed without any adjustment, even the classical music (the supreme and killing test) If you like natural sound with transparent dynamic processing, without pumping effect, this piece is for you.


Wanna have your own page here, write about your own experiences, own review, refute existing review,
add comments to existing review, publish your circuits ?
Contact me


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