Amplifier for 100 watt 12volt shortwave

[cburger]

In an effort to boost signal distance on 20 and 40 meter I am wondering if it would be logical to install a 12 volt amplifier for on board shortwave radio and if so what wattage and brand might be a good choice?

[AA3JY]

Depending on your battery capacity...

https://www.universal-radio.com/catalog/amps/3552.html

[cburger]

Thank you looks like really quality amp, maybe don't have to go to 500 watts?

[Brian.D]

I would think the best "booster" for your rig is a really good antenna and ground/counterpoise. Plus, having a good solar cycle doesn't hurt either. But...

[ronstory]

Hmmm... what is the power you are using now?

[Bycrick]

I can’t imagine a case where the extra power of a amplifier (beyond the 100 watts or so from most radios) is going to help with most antennas that you could fit on a sailboat. Especially for Pactor, a lot of power isn’t necessary. I’ve usually throttled my various Icom radios over the years back to 50-70% power and had good communications all over the West Coast of the Americas and on crossings to Tahiti and Hawaii.

[Scott Berg]

I use an SGC 500 Cube Amp (about 500w on phone, 300 cw). It makes a 2+ s unit difference on 20, a shade more on 40, in most cases. 6db is a lot and while it isn't necessary for digital modes like pactor it does help with DX. My primary 20m antenna is a vertical dipole (Coax Fed, cut to 14.300) and my primary 40m is a wire antenna made up of mizzen cap shroud jumped to triatic stay. I use a Palstar tuner @ the rig right now, plan to upgrade to an SG235 at some point to automate tuning. Not necessary for marine comms in most cases but it does make the /mm shack break pile up's a lot more easily. YMMV but after 50 years I've decided that in most cases aboard, life is too short for QRP. Of course I love my FT817, but not as a boat based radio most of the time... 73 WAØLSS /MM

[waterman46]

Originally Posted by Brian.D

I would think the best "booster" for your rig is a really good antenna and ground/counterpoise. Plus, having a good solar cycle doesn't hurt either. But...

Very True. And I think your best information source would be in the ham radio community, looking for mobile equipment and experiences with same.

I too have wondered about adding a final amp to my onboard ham rig. I came to same conclusion as above, and reasoned that the power requirements just don't really make it worthwhile. Remember you need to receive over the same path you are sending, so even if you have a huge signal going out, if you can't improve reception it won't help too much.

I also worry about increased RF on board doing damage to sensitive equipment in particular the autopilot's compass and all GPS receivers.

[Parrothedd]

The SGC 500 Cube Amp Scott Burg referred to is an awesome little amp.

[cburger]

Thanks all for replies here. Vessels HF equipment is 100 watts, antenna tuner to end fed back stay, Kiss for ground. I am new to all this and am enjoying the learning curve. My vessel is currently on hard for extensive repairs and I mess around with trying to raise hams on different bands. The last attempt was trying to reach Cruisers Net control in Houston, Tx. with the operator indicating he couldn't pull me out of the "Slop", considering he was over 1600 miles away from me in NY I thought that was pretty good and maybe a little more wattage would of made a difference. When I can find the time would like to install dedicated vertical antennas optimized for 20 and 40. Very often on 20 meters can here incoming signal crystal, and cant raise sender.

[Brian.D]

While you are on the hard, you might take this down time cleaning/replacing all your rf connections. A little PM goes a long way.

Also you might want to run WSPR @ 5 watts. That will let you know who is hearing you and who you are hearing. Yeah, I know, who wants to work QRP, but it is a good indicator of how you system is working.

[S/V Illusion]

Do as Brian suggested.

Going from 100 to 500 watts will increase your signal by 3 -4 dB which is virtually indiscernible. To increase your signal by 2 S units ( 12 dB), you would have to increase power by a factor of almost 20, i.e., 2000 watts. Clearly impracticable not to mention illegal.

The best improvement you can make is good quality, new, low loss coax, quality connectors and a resonant antenna to obviate tuner loss.

[Catboat Willy]

I think others have said this quite successfully. Get to improving the antenna system. Too much RF floating around your boat, especially with a higher SWR, may have a detrimental effect on the other sensitive equipment aboard. If you can't work it with 100 watts, you'll probably do a poor job with 1000. The bang will not be worth it.
73's
W2CWL

[KP44]

What others have said. ….
We are mandated to use no more power than necessary. An antenna matched to your frequencies and lead-in with minimal standing wave will do much better than a linear amp. Look at MFJ antenna tuners if you don't have an Icom or other tuner.

[Stewie12]

To amplify 100% of nothing is still 100% of nothing. You need a good signal. Think about making a centre fed dipole to the frequency you want to use instead of using your back stay. String it up alongside.