Messages

1

European Pirates and Private Stations / Enterprise Radio 6950 AM 0710 UTC 05 FEB 2023

« on: February 05, 2023, 0756 UTC »

Italian pirate station, could be the only present on air. Selection of old pop italian songs at 07.15 UTC SINPO 44444

ID at 07.58: "Questa è la tua radio libera in onde corte, Enterprise Radio" (This is your free station on shortwave, ER) follow song from Ivan Graziani "Firenze (canzone triste)"

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European Pirates and Private Stations / Re: UNID 6380 AM 2217 UTC 12 Jun 2022

« on: June 12, 2022, 2229 UTC »

6380 is WMBR Radio from northern Holland. They was online yesterday night too.

3

The RF Workbench / Re: Someone had Corsair II AM TX experience?

« on: January 24, 2017, 1318 UTC »

In the end altough I have made so much tweakening and modification, modulation quality was not better than average-mediocre. So I have decided to change completely the modulation type from "low level" to a more classic "high level" directly on the final mosfet, using a simple serial modulator built between a little SMD TDA2030 AF Module (you find very easily on Ebay or Ali or Bang for pennies, like this: http://www.ebay.it/itm/TDA2030A-Audio-Amplificatore-18W-6-12V-Amplifier-Arduino-Module-Board-/252397102253?hash=item3ac40a24ad:g:9lMAAOSwq5pXP19y) and a good 2N3055 TO-3 transistor with a radiator. This was taken out from the open source book "Low Power AM Handbook". This design involving you raise the power supply for TDA2030 AF module, 2N3055 transistor and RF final IRF530N mosfet to 24V and almost 3A, so you need to put a 7812 linear regulator (with radiator too) to supply DDS module, BF245 and BS170 stage. Now modulation is very clear and somewhat more RF power out! To adapt a normal potentiometer to AF module I have literally cut out its 10K trimmer leaving some mm of old connectors to solder up new connection for the new 47 Kohm linear panel potentiometer.

Hi F.

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The RF Workbench / Re: Someone had Corsair II AM TX experience?

« on: January 07, 2017, 1822 UTC »

Interesting that ground loop question. I will try battery operated, however (I don't know if it count) audio source come all from battery operated device (CD Player, Smartphone MP3 player).

Thanks, F.

5

The RF Workbench / Re: Someone had Corsair II AM TX experience?

« on: January 05, 2017, 2346 UTC »

Oh, this was an old prototype when I was thinking final Mosfet become hot like hell and in the back of heatsink put a PC fan  Now is a simple heatsink in the back of metallic box...

I think that problem in the end is the impedance mismatch from AF input through LM386+TIP31C to intermediate Mosfet BS170 and then to final mosfet. When I was testing, with an higher impedance signal injector square wave input signal (without transformer) audio was clear and no distorted. Could be instead use a 1:1 audio transformer same result can be achieved with a little one-transistor preamplifier in front of LM386 input...

Ciao F.

6

The RF Workbench / Re: Someone had Corsair II AM TX experience?

« on: January 05, 2017, 1158 UTC »

Ok, I have tweakening schematic doing many many tests and finally I think to have found what was wrong. In schematic AF output of LM386+TIP31C pass through a 17 uH inductance (L2 in schematic) in parallel with 560 Ohm resistor (R5) to BS170 drain. I have eliminate the resistor and substitute the 17 uH 1/2W "resistor-like" inductance I had placed before with a red toroid (T50/2) with 59 turns of 0.3 mm (AWG 28) copper wire.

But the real problem to solve was to separate input AF to LM386 input, so I have added a 1:1 600 ohm audio transformer, with one side directly connected to one RCA input, isolated from ground and other side connect to input of transmitter.

Now modulation is good (see short video linked) normal BIAS regulation without rustles and whistles, IRF530N power mosfet runs from warm to moderately hot depends from BIAS voltage, reach nominal 10W output, 1-1,3 A absorption.

https://youtu.be/DN_Q6t4k530

7

The RF Workbench / Re: Someone had Corsair II AM TX experience?

« on: January 03, 2017, 0915 UTC »

Thank you Moof, so you confirm to me that anyone of three Corsair version appearing on Dave Martin's blog is really good working in modulation stage, neither that one use a transistor driver instead latest version with BS170 mosfet. Yes I have tried to change BIAS settings in all way possible, but only with voltage set very very low, modulation quality seems acceptable, so I have tried too to isolate AF LM386 stage before and LM 386+TIP31C stage from rest of transmitter and AF tone until there is regular. Well, what can I say? I will tried "last resort" to consult some experienced HAM in my neighborhood but better will be soon that faulty schemes disappear, 'cause we don't need garbage not really well tested and working that makes you waste time and money.

Thank you.

8

The RF Workbench / Someone had Corsair II AM TX experience?

« on: January 01, 2017, 2339 UTC »

Hi all, HI, I have made a Corsair II transmitter for MW operation (see pic attached) with a VFO DDS variant and power out is no problem, but modulation is always dirty and distorted at every input AF level, expecially when its transmitting music. Problem I think is in the LM386-TIP31C-BS170 section, because I have tried back xtal oscillator instead VFO DDS drive with always same result: power strenght is ok but modulation is distorted and coarse. I have tried to modify LM386 gain and/or to indrease R3 to 1,2 Kohm with no appreciated results. Someone that tried to built same transmitter could you give me some clue?

Have a good 2017. F.