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Author Topic: Starting a pirate radio in Spain  (Read 1862 times)

Offline diegocollado

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Starting a pirate radio in Spain
« on: July 14, 2018, 1547 UTC »
Hello everybody! I'm a new user here at hfUnderground after lurking around for some time now. I'm an 18 year old Ham radio operator and SW listener. I've been wanting to start a pirate radio for a couple of years, but never had the time, money or guts necessary to start the project, but now I've got all those three things. I've decided that I would love to start a low power one, enough to cover some cities around me (I'm from Barcelona, Spain), but I've still got a lot to learn in regards to transmitter building and other things. Now, I've got a microphone, a mixing board and a computer, meaning that the only things left would be the transmitter and the antenna, right? Which transmitters and antennas do you guys recommend? I've been looking at shortwave, but also at medium wave, as it is more popular that shortwave in Spain. What do you recommend I start with? Budget is rather small, as I'm a student.

Best regards,
Diego

Offline East Troy Don

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Re: Starting a pirate radio in Spain
« Reply #1 on: July 14, 2018, 1736 UTC »
Wow....another economically struggling student - we've all been there!   Anyway, maybe this will help you:
http://freemedia.blogspot.com/2012/09/how-to-set-up-pirate-radio-station-in.html
Primary: Yaesu FRG-7700  Secondary: ICOM R75 Tertiary: Grundig  750. Sangean ATS-909X .  Alpha Delta  SWL Sloper antenna. : Also, 1940 Mantola am/sw tube.   QTH: East Troy Wisconsin  USA.  Sea Level: + 320 meters .  90 miles (but not far enough) NNW of Chicago

Offline OgreVorbis

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Re: Starting a pirate radio in Spain
« Reply #2 on: July 15, 2018, 0122 UTC »
I would say go with shortwave or FM, but not AM (MW). Getting an effective antenna set up for AM is hard. You need a lot of space. There any many designs for shortened AM antennas, but none of them work well. You'll go farther with the same power on FM. If you do have the space for a massive antenna, then go with AM. You'll find the range to be really good if you use the right antenna. I know this from experience.

To decide between FM and shortwave, you have to think about your target audience. Is it a bunch of radio geeks from around the world, or is it the average local person?

If you want a good FM transmitter: pcs-electronics or "The Radiomaster"
If you're looking for a SW: Stretchyman or https://www.ebay.com/itm/DDS-AM-LW-MW-SW-TRANSMITTER-MODULATOR-100KHz-30MHz-AUTO-LPF-BPF/323346484122
... then you can just get an HF linear amp and you'll cover MW and shortwave with the same transmitter.

The PWMs are better, so if you looking for higher power and more efficiency, then take a look at stretchyman instead. But for low power a linear amp should be fine (and more broadband).
Radio and Programming Blog: http://dosaidsoft.com/wp/

Offline OgreVorbis

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Re: Starting a pirate radio in Spain
« Reply #3 on: July 15, 2018, 0127 UTC »
Another thing to keep in mind about the effectiveness of AM: You should look up what the ground conductivity is in your area. I am in the US and it is 0.5 - 1 here (i forgot what units it's in). It seems to be on average 10. If it's low, AM won't work well in your area because it travels by groundwave. This might be a good way to decide if you want to do it. The difference is huge. Where I live now, a 1kw AM station only goes 6-8 miles!!! I used to live in another part of the US and stations with 1kw can go up to 100 miles.
Radio and Programming Blog: http://dosaidsoft.com/wp/

Offline diegocollado

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Re: Starting a pirate radio in Spain
« Reply #4 on: July 15, 2018, 2120 UTC »
I would say go with shortwave or FM, but not AM (MW). Getting an effective antenna set up for AM is hard. You need a lot of space. There any many designs for shortened AM antennas, but none of them work well. You'll go farther with the same power on FM. If you do have the space for a massive antenna, then go with AM. You'll find the range to be really good if you use the right antenna. I know this from experience.

To decide between FM and shortwave, you have to think about your target audience. Is it a bunch of radio geeks from around the world, or is it the average local person?

If you want a good FM transmitter: pcs-electronics or "The Radiomaster"
If you're looking for a SW: Stretchyman or https://www.ebay.com/itm/DDS-AM-LW-MW-SW-TRANSMITTER-MODULATOR-100KHz-30MHz-AUTO-LPF-BPF/323346484122
... then you can just get an HF linear amp and you'll cover MW and shortwave with the same transmitter.

The PWMs are better, so if you looking for higher power and more efficiency, then take a look at stretchyman instead. But for low power a linear amp should be fine (and more broadband).

Dear OgreVorbis,
Thank you very much for your detailed reply, I really appreciate it.

Regarding FM, I've pretty much discarded that option as all of the FM frequencies in my city are taken and authorities are really strict on that.

On the other hand, AM is pretty empty yet available everywhere (cars, most radios...). I live in an apartment block, so the only place I would be able to set up a MW antenna would be on the rooftop, so no buring ground sticks (those metal things, sorry for the lack of vocabulary) and space could be a little bit of a problem. How big are we talking about? Would a 1/4 dipole in an inverted vee work?

I've considered shortwave and I've talked with Stretchyman about it. I don't really have the budget to spend on a powerful transmitter, so I'd be TXing low power with one of his transmitters (I'm still learning about building one and I wouldn't want to mess it up, so building one myself is not an option, currently), meaning that I maybe wouldn't be able to reach very far, yet also wouldn't make it locally due to the skip.
What do you recommend? I'm still doubting about which route to take.

Again, thank you so much for your help.
Best regards,
Diego

« Last Edit: July 15, 2018, 2145 UTC by diegocollado »

Offline diegocollado

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Re: Starting a pirate radio in Spain
« Reply #5 on: July 15, 2018, 2125 UTC »
Another thing to keep in mind about the effectiveness of AM: You should look up what the ground conductivity is in your area. I am in the US and it is 0.5 - 1 here (i forgot what units it's in). It seems to be on average 10. If it's low, AM won't work well in your area because it travels by groundwave. This might be a good way to decide if you want to do it. The difference is huge. Where I live now, a 1kw AM station only goes 6-8 miles!!! I used to live in another part of the US and stations with 1kw can go up to 100 miles.

It seems to be between 2 and 4, so I don't think it might work really well...

Offline ThaDood

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Re: Starting a pirate radio in Spain?
« Reply #6 on: July 15, 2018, 2320 UTC »
One question is, when do you plan to broadcast, day, or night? If it is nighttime, then the upper MW and lower SW bands will always get you out there, especially in winter when thunderstorm lightning crash static is way lower. Right now, in mid-July, MW and lower HF bands suck with nothing but lightning crashes at night. If you are looking at daytime, the HF low bands will get you out regionally, while the mid-HF bands are come and go, 31M, 25M, 22M, and 19M, bands. Being that we are in the bottom of a sunspot cycle, upper HF bands really suck now, with the exception of Sporadic E on the 11M Broadcast band, 25.670MHz - 26.100MHz. But, that too is so hit and miss. (Albeit, a good way to stay one step ahead of the country's monitoring authorities.) However, around 13MHz, (22M), with no skip that band has a decent local coverage with a few watts going to a vertical antenna. What is interesting is that I'm starting to see more International Broadcast Stations start up in this band, so there must be something to that. One thing that you do not want to do is to broadcast in one place for too long, or you are an easy target, sitting duck. If possible, have a mobile set up, where you can goto several parks, and do a quick broadcast that way. You have a studio set up? Make up pre-recorded podcast-like programs to air later. In North America, hit and run gorilla warfare-like broadcasting has been done for decades to elude the FCC and DOC. Now, as far as gear to start off with? Many started out with what was called Boat Anchors, a.k.a. 1950's - 1960's tube gear that was so discarded in the 1980's and and 1990's for dirt cheap. You still may find classic tube gear for the HF bands. That is changing today where these rigs are now collectibles where they are collecting top dollar, or Euros, for them. Still, you may be able to find at junk stores, flea-markets, hamfests, and even estate sales, people wanting to get rid of these rigs for cheap, but time is ticking there. And, if there is not too much wrong with a rig, you can repair the problems yourself, and rock 'n roll on-air. BTW, not me, but someone very closely resembling me, may have had experience with all this. Transmisión feliz, ˇy setenta y tres!
I can't decide upon what's worst, young and stupid, or old and chemically dumbed down.

Offline OgreVorbis

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Re: Starting a pirate radio in Spain
« Reply #7 on: July 16, 2018, 0016 UTC »

Dear OgreVorbis,
Thank you very much for your detailed reply, I really appreciate it.

Regarding FM, I've pretty much discarded that option as all of the FM frequencies in my city are taken and authorities are really strict on that.

On the other hand, AM is pretty empty yet available everywhere (cars, most radios...). I live in an apartment block, so the only place I would be able to set up a MW antenna would be on the rooftop, so no buring ground sticks (those metal things, sorry for the lack of vocabulary) and space could be a little bit of a problem. How big are we talking about? Would a 1/4 dipole in an inverted vee work?

I've considered shortwave and I've talked with Stretchyman about it. I don't really have the budget to spend on a powerful transmitter, so I'd be TXing low power with one of his transmitters (I'm still learning about building one and I wouldn't want to mess it up, so building one myself is not an option, currently), meaning that I maybe wouldn't be able to reach very far, yet also wouldn't make it locally due to the skip.
What do you recommend? I'm still doubting about which route to take.

Again, thank you so much for your help.
Best regards,
Diego

In terms of antennas:
For SW, an inverted V is probably my favorite because it doesn't take up too much space and only requires one support. The skywave propagation with them is also pretty good.

For MW:
I've tried a full half wave inverted V - this was huge and the local coverage was poor, but I was able to tune into myself from an SDR about 500 miles away. (This was with 300W on 1710). The local coverage was only 2 miles interestingly.
Isotron - the worst
Long wire - second worst
1/4 wave ground plane - the best (this was temporary because I had to use a balloon to raise the wire)

If you want local, you'll need a vertical antenna. I don't know how high your block is, but maybe hanging an antenna from the roof instead of trying to fit it on top would be better. The ideal situation would be if you were on the middle floor of a tall building because then you could put the center of the dipole out the window and have one leg run up to the roof and let the other hang to the ground.

EDIT: If you decide to go with MW, you're likely going to need an antenna tuner. Unless your antenna is in the middle of a field, the surrounding objects will make it not resonate at the proper frequency. There is a formula to calculate the length, but you'll find that on MW the calculation ends up being so much different than the actual length the antenna needs to be. With shortwave, as long as you have an SWR analyzer, you won't need a tuner because generally, you can just cut the ends of the V until you get it perfect.

I also really recommend that transmitter I linked to in my other post. It will work on both MW and SW, so you won't need to buy another transmitter if you change your mind. You'll need an amplifier for it though because it only makes 1mW.

You should also check out VOACAP btw. You put in your location and a few other parameters and it will give you a theoretical coverage map. You can select the frequency and do it again to see the difference in propagation.
« Last Edit: July 16, 2018, 0035 UTC by OgreVorbis »
Radio and Programming Blog: http://dosaidsoft.com/wp/

Offline diegocollado

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Re: Starting a pirate radio in Spain
« Reply #8 on: July 16, 2018, 1720 UTC »

Dear OgreVorbis,
Thank you very much for your detailed reply, I really appreciate it.

Regarding FM, I've pretty much discarded that option as all of the FM frequencies in my city are taken and authorities are really strict on that.

On the other hand, AM is pretty empty yet available everywhere (cars, most radios...). I live in an apartment block, so the only place I would be able to set up a MW antenna would be on the rooftop, so no buring ground sticks (those metal things, sorry for the lack of vocabulary) and space could be a little bit of a problem. How big are we talking about? Would a 1/4 dipole in an inverted vee work?

I've considered shortwave and I've talked with Stretchyman about it. I don't really have the budget to spend on a powerful transmitter, so I'd be TXing low power with one of his transmitters (I'm still learning about building one and I wouldn't want to mess it up, so building one myself is not an option, currently), meaning that I maybe wouldn't be able to reach very far, yet also wouldn't make it locally due to the skip.
What do you recommend? I'm still doubting about which route to take.

Again, thank you so much for your help.
Best regards,
Diego

In terms of antennas:
For SW, an inverted V is probably my favorite because it doesn't take up too much space and only requires one support. The skywave propagation with them is also pretty good.

For MW:
I've tried a full half wave inverted V - this was huge and the local coverage was poor, but I was able to tune into myself from an SDR about 500 miles away. (This was with 300W on 1710). The local coverage was only 2 miles interestingly.
Isotron - the worst
Long wire - second worst
1/4 wave ground plane - the best (this was temporary because I had to use a balloon to raise the wire)

If you want local, you'll need a vertical antenna. I don't know how high your block is, but maybe hanging an antenna from the roof instead of trying to fit it on top would be better. The ideal situation would be if you were on the middle floor of a tall building because then you could put the center of the dipole out the window and have one leg run up to the roof and let the other hang to the ground.

EDIT: If you decide to go with MW, you're likely going to need an antenna tuner. Unless your antenna is in the middle of a field, the surrounding objects will make it not resonate at the proper frequency. There is a formula to calculate the length, but you'll find that on MW the calculation ends up being so much different than the actual length the antenna needs to be. With shortwave, as long as you have an SWR analyzer, you won't need a tuner because generally, you can just cut the ends of the V until you get it perfect.

I also really recommend that transmitter I linked to in my other post. It will work on both MW and SW, so you won't need to buy another transmitter if you change your mind. You'll need an amplifier for it though because it only makes 1mW.

You should also check out VOACAP btw. You put in your location and a few other parameters and it will give you a theoretical coverage map. You can select the frequency and do it again to see the difference in propagation.

Dear OgreVorbis,
Thank you very much for your detailed reply, I really appreciate it.

Regarding FM, I've pretty much discarded that option as all of the FM frequencies in my city are taken and authorities are really strict on that.

On the other hand, AM is pretty empty yet available everywhere (cars, most radios...). I live in an apartment block, so the only place I would be able to set up a MW antenna would be on the rooftop, so no buring ground sticks (those metal things, sorry for the lack of vocabulary) and space could be a little bit of a problem. How big are we talking about? Would a 1/4 dipole in an inverted vee work?

I've considered shortwave and I've talked with Stretchyman about it. I don't really have the budget to spend on a powerful transmitter, so I'd be TXing low power with one of his transmitters (I'm still learning about building one and I wouldn't want to mess it up, so building one myself is not an option, currently), meaning that I maybe wouldn't be able to reach very far, yet also wouldn't make it locally due to the skip.
What do you recommend? I'm still doubting about which route to take.

Again, thank you so much for your help.
Best regards,
Diego

In terms of antennas:
For SW, an inverted V is probably my favorite because it doesn't take up too much space and only requires one support. The skywave propagation with them is also pretty good.

For MW:
I've tried a full half wave inverted V - this was huge and the local coverage was poor, but I was able to tune into myself from an SDR about 500 miles away. (This was with 300W on 1710). The local coverage was only 2 miles interestingly.
Isotron - the worst
Long wire - second worst
1/4 wave ground plane - the best (this was temporary because I had to use a balloon to raise the wire)

If you want local, you'll need a vertical antenna. I don't know how high your block is, but maybe hanging an antenna from the roof instead of trying to fit it on top would be better. The ideal situation would be if you were on the middle floor of a tall building because then you could put the center of the dipole out the window and have one leg run up to the roof and let the other hang to the ground.

EDIT: If you decide to go with MW, you're likely going to need an antenna tuner. Unless your antenna is in the middle of a field, the surrounding objects will make it not resonate at the proper frequency. There is a formula to calculate the length, but you'll find that on MW the calculation ends up being so much different than the actual length the antenna needs to be. With shortwave, as long as you have an SWR analyzer, you won't need a tuner because generally, you can just cut the ends of the V until you get it perfect.

I also really recommend that transmitter I linked to in my other post. It will work on both MW and SW, so you won't need to buy another transmitter if you change your mind. You'll need an amplifier for it though because it only makes 1mW.

You should also check out VOACAP btw. You put in your location and a few other parameters and it will give you a theoretical coverage map. You can select the frequency and do it again to see the difference in propagation.

Dear OgreVorbis,
Thank you once again for such an informative reply. I'm learning a lot from posts like this.

I think I will go with SW for now, as the antenna will be easier to set up, more discreet. Regarding the transmitter you linked on your previous post, what would be the maximum power recommended with an HF linear amp? Would something like this https://m.ebay.com/itm/2MHZ-30MHZ-50W-HF-linear-amplifier-RF-power-AMP-13-56MHZ-shortwave-transmit/272762087295?epid=19005363907&hash=item3f81e3277f%3Ag%3A%7EuUAAOSwlRpZaKRO&_nkw=hf+linear+amp+am&_sacat=163853&_from=R40&rt=nc&_trksid=m4084.l1313 work? If not, what amps do you recommend and how many watts? Would I need anything else, like filters? If so, would they be easy to build or obtain?

Thank you for the VOACAP website, as it seems to be a very useful resource.

And again, thanks for the detailed posts.

Best regards,
Diego

Offline Stretchyman

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Re: Starting a pirate radio in Spain
« Reply #9 on: July 16, 2018, 1901 UTC »
The Chinese stuff is utter rubbish. Just get something with BLR188XR. Sure not cheap but will push 800W+ with a 3W i/p.

Str.
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline OgreVorbis

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Re: Starting a pirate radio in Spain
« Reply #10 on: July 17, 2018, 0334 UTC »
Dear OgreVorbis,
Thank you once again for such an informative reply. I'm learning a lot from posts like this.

I think I will go with SW for now, as the antenna will be easier to set up, more discreet. Regarding the transmitter you linked on your previous post, what would be the maximum power recommended with an HF linear amp? Would something like this https://m.ebay.com/itm/2MHZ-30MHZ-50W-HF-linear-amplifier-RF-power-AMP-13-56MHZ-shortwave-transmit/272762087295?epid=19005363907&hash=item3f81e3277f%3Ag%3A%7EuUAAOSwlRpZaKRO&_nkw=hf+linear+amp+am&_sacat=163853&_from=R40&rt=nc&_trksid=m4084.l1313 work? If not, what amps do you recommend and how many watts? Would I need anything else, like filters? If so, would they be easy to build or obtain?

Thank you for the VOACAP website, as it seems to be a very useful resource.

And again, thanks for the detailed posts.

Best regards,
Diego

That Chinese one needs about 1-5W input I think, so it won't work.

Here are some options that all support around 1mW input:
https://www.ebay.com/itm/10W-HF-PA-10-watts-13-5v-HF-amplifier-for-HAM-radio-CW-SSB-FM-digital/332237134236?hash=item4d5ae0599c:g:LcEAAOSwux5YNJ3f
https://www.ebay.com/itm/20W-HF-PA-20-watts-24v-HF-amplifier-for-HAM-radio-CW-SSB-FM-digital/332643829840
https://www.ebay.com/itm/50-Watt-SSB-linear-Power-Amplifier-for-transceiver-intercom-Radio-HF-FM-CW/252126056815
https://www.ebay.com/itm/100W-HF-PA-RD100HHF1-13-5v-HF-amplifier-HAM-radio-CW-SSB-FM-DIGI-1-55-MHz/332672297281?hash=item4d74d06941:g:OTsAAOSwScJbEolE

Filter:
https://www.ebay.com/itm/LPF-300W-1-8-54MHz-low-pass-filter-1-pc-for-1-band/151916768969
(You specify what band you want, so assuming you want to test 69xx khz, say the 40m band filter.)

The third one I listed there is the cheapest, but it Chinese, so it may not do what you want. It says 1-5mW input, so it might produce less power than they claim with only 1mW. The other three are more expensive, but they should work as advertised.

I don't know how much you know about this, but you should be aware that when modulating AM, you set the power to 1/4 of what the amplifier can produce and then the audio will peak it to full power. Most of these have a PTT (push to talk), so you have to remember to short it to make the TX work all the time.
Radio and Programming Blog: http://dosaidsoft.com/wp/

Offline diegocollado

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Re: Starting a pirate radio in Spain?
« Reply #11 on: July 17, 2018, 1650 UTC »
One question is, when do you plan to broadcast, day, or night? If it is nighttime, then the upper MW and lower SW bands will always get you out there, especially in winter when thunderstorm lightning crash static is way lower. Right now, in mid-July, MW and lower HF bands suck with nothing but lightning crashes at night. If you are looking at daytime, the HF low bands will get you out regionally, while the mid-HF bands are come and go, 31M, 25M, 22M, and 19M, bands. Being that we are in the bottom of a sunspot cycle, upper HF bands really suck now, with the exception of Sporadic E on the 11M Broadcast band, 25.670MHz - 26.100MHz. But, that too is so hit and miss. (Albeit, a good way to stay one step ahead of the country's monitoring authorities.) However, around 13MHz, (22M), with no skip that band has a decent local coverage with a few watts going to a vertical antenna. What is interesting is that I'm starting to see more International Broadcast Stations start up in this band, so there must be something to that. One thing that you do not want to do is to broadcast in one place for too long, or you are an easy target, sitting duck. If possible, have a mobile set up, where you can goto several parks, and do a quick broadcast that way. You have a studio set up? Make up pre-recorded podcast-like programs to air later. In North America, hit and run gorilla warfare-like broadcasting has been done for decades to elude the FCC and DOC. Now, as far as gear to start off with? Many started out with what was called Boat Anchors, a.k.a. 1950's - 1960's tube gear that was so discarded in the 1980's and and 1990's for dirt cheap. You still may find classic tube gear for the HF bands. That is changing today where these rigs are now collectibles where they are collecting top dollar, or Euros, for them. Still, you may be able to find at junk stores, flea-markets, hamfests, and even estate sales, people wanting to get rid of these rigs for cheap, but time is ticking there. And, if there is not too much wrong with a rig, you can repair the problems yourself, and rock 'n roll on-air. BTW, not me, but someone very closely resembling me, may have had experience with all this. Transmisión feliz, ˇy setenta y tres!

Dear ThaDood,
Sorry for the late reply. I was on mobile and I must have sadly skipped over your reply. Thank you very much for your message. I plan on broadcasting at night and according to VOACAP, a good band would be 60m. Do you recommend it?
I will take a look at the "boat anchors" you mention. I have a studio set up, so recording podcast-like is no problem.

Again, thank you for your very helpful advice.
ˇSetenta y tres!

Offline diegocollado

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Re: Starting a pirate radio in Spain
« Reply #12 on: July 17, 2018, 1651 UTC »
The Chinese stuff is utter rubbish. Just get something with BLR188XR. Sure not cheap but will push 800W+ with a 3W i/p.

Str.

Will take a look at it! Thank you, Stretchyman! (although it looks like it's a bit out of my budget, sadly  :'( )

Offline diegocollado

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Re: Starting a pirate radio in Spain
« Reply #13 on: July 17, 2018, 1658 UTC »
Dear OgreVorbis,
Thank you once again for such an informative reply. I'm learning a lot from posts like this.

I think I will go with SW for now, as the antenna will be easier to set up, more discreet. Regarding the transmitter you linked on your previous post, what would be the maximum power recommended with an HF linear amp? Would something like this https://m.ebay.com/itm/2MHZ-30MHZ-50W-HF-linear-amplifier-RF-power-AMP-13-56MHZ-shortwave-transmit/272762087295?epid=19005363907&hash=item3f81e3277f%3Ag%3A%7EuUAAOSwlRpZaKRO&_nkw=hf+linear+amp+am&_sacat=163853&_from=R40&rt=nc&_trksid=m4084.l1313 work? If not, what amps do you recommend and how many watts? Would I need anything else, like filters? If so, would they be easy to build or obtain?

Thank you for the VOACAP website, as it seems to be a very useful resource.

And again, thanks for the detailed posts.

Best regards,
Diego

That Chinese one needs about 1-5W input I think, so it won't work.

Here are some options that all support around 1mW input:
https://www.ebay.com/itm/10W-HF-PA-10-watts-13-5v-HF-amplifier-for-HAM-radio-CW-SSB-FM-digital/332237134236?hash=item4d5ae0599c:g:LcEAAOSwux5YNJ3f
https://www.ebay.com/itm/20W-HF-PA-20-watts-24v-HF-amplifier-for-HAM-radio-CW-SSB-FM-digital/332643829840
https://www.ebay.com/itm/50-Watt-SSB-linear-Power-Amplifier-for-transceiver-intercom-Radio-HF-FM-CW/252126056815
https://www.ebay.com/itm/100W-HF-PA-RD100HHF1-13-5v-HF-amplifier-HAM-radio-CW-SSB-FM-DIGI-1-55-MHz/332672297281?hash=item4d74d06941:g:OTsAAOSwScJbEolE

Filter:
https://www.ebay.com/itm/LPF-300W-1-8-54MHz-low-pass-filter-1-pc-for-1-band/151916768969
(You specify what band you want, so assuming you want to test 69xx khz, say the 40m band filter.)

The third one I listed there is the cheapest, but it Chinese, so it may not do what you want. It says 1-5mW input, so it might produce less power than they claim with only 1mW. The other three are more expensive, but they should work as advertised.

I don't know how much you know about this, but you should be aware that when modulating AM, you set the power to 1/4 of what the amplifier can produce and then the audio will peak it to full power. Most of these have a PTT (push to talk), so you have to remember to short it to make the TX work all the time.

Dear OgreVorbis,
Thank you very much once again for your very informative message.
I will take a look at those amps you linked. Sorry if I'm asking too many questions, but would you recommend I acquire or try to assemble an audio compressor? Would a software one work?

Thanks and best regards,
Diego

Offline OgreVorbis

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Re: Starting a pirate radio in Spain
« Reply #14 on: July 18, 2018, 0057 UTC »
Dear OgreVorbis,
Thank you very much once again for your very informative message.
I will take a look at those amps you linked. Sorry if I'm asking too many questions, but would you recommend I acquire or try to assemble an audio compressor? Would a software one work?

Thanks and best regards,
Diego

Not a problem. Stereo tool is a good one. It has compression and limiting and it also has an adjustable low pass filter for the audio, which should be set around 3-7 khz. The lower you set it, the signal will go a little farther, but the audio quality is obviously less.

I use a DSP board from China that has a ADAU1701. I've also used stereo tool in the past, but I've had audio buffering problems with it. It seems like it works fine as long as you don't use a virtual audio cable to route the audio within the computer. You should use a physical audio cable. The problem with this is that the computer can no longer be a sound source because its output is the stereo tool only. So if you have another sound source (or another sound card) and a mixer, etc. Then you just put that into the line-in of the comp and the output to the TX.
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