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linear amplifier

Posted: 22 May 2020, 16:57
by Flat_Battery
I appreciate there are people here who have forgot more about radio than I have learnt during covid-19. Having come back to this 35 after.

Currently my set kicks out about 35W SSB peak, I am using an halfwave about 4m off the ground with no near build withs the exception of a very big tree( geographically it would be Svalbard I would be missing), but other than that am good. I live in a slight valley. I am looking for a linear amplifier, nothing outlandish for 27/28 mhz.

Any suggestions, thought?

Thanks

FB

Re: linear amplifier

Posted: 22 May 2020, 17:22
by ch25
To have 1s unit signal improvement power x4 means KL203
To have 2s signal improvement power x16 means KL703
As simple as that.
Chris

Re: linear amplifier

Posted: 22 May 2020, 17:39
by Flat_Battery
Thanks Lemmy, would this need a 15a power supply to drive this with no issues and if so is there any special I would need to be aware of?

FB

Re: linear amplifier

Posted: 22 May 2020, 18:31
by ch25
If we talk about KL203 15A is enough, but...
1. You have to put some fan on top, computer 12V fan will do the trick.
2. You must lower drive power to 2W AM/FM, 12W SSB, otherwise it will sound raspy and you will fry this amp within minutes.
Chris

Re: linear amplifier

Posted: 22 May 2020, 19:56
by The Collector
I know very little about amp's, but I know there are bog-standard, cheap messy amp's and there are good quality class A/B type ones. You get what you pay for. You can get a cheap 200watt FM/AM amp for £45, or a good quality 70watt one for £150. It depends how clean you want your audio, how much wattage you want to push and how much you want to spend. Also, if you want 12/24v or mains powered. I think the RM amp's are cheap and cheerful, but do a reasonable job. A few people on here have mentioned the 203 before now.

There have probably been a few topics about them on here before, so if you don't get much joy response-wise, perhaps have a go with the search feature.

Re: linear amplifier

Posted: 22 May 2020, 23:11
by 108EH002
A kl203 has lasted many years for me (not minutes),and that was running about 4/5w am/fm and about 15w max on ssb,just make sure the swr is low and keep the overs short.

If you intend to run a bit more power,I would also consider getting your antenna as high as possible.

You will increase the receive if you get the halfwave much higher up if you can.

No point getting out a bit better if you are possibly going to be toiling on the receive.

The antenna is going to be well below the nearby rooflines at 4m off the ground like at present.

4m will be ok for dxing but the extra height and hassle is worth the effort for local/groundwave contacts.

Re: linear amplifier

Posted: 23 May 2020, 05:54
by QRZ-934
108EH002 wrote:
22 May 2020, 23:11
A kl203 has lasted many years for me (not minutes),and that was running about 4/5w am/fm and about 15w max on ssb,just make sure the swr is low and keep the overs short.

If you intend to run a bit more power,I would also consider getting your antenna as high as possible.

You will increase the receive if you get the halfwave much higher up if you can.

No point getting out a bit better if you are possibly going to be toiling on the receive.

The antenna is going to be well below the nearby rooflines at 4m off the ground like at present.

4m will be ok for dxing but the extra height and hassle is worth the effort for local/groundwave contacts.
Recently got a kl503, supposed to be 250-300watts...is it heck! :D
Actual max measured output is 140watts FM but it gets warm fast on that mode, am and ssb are around 130 watts and its only luke warm to the touch.
Have hit loads of places in europe over the past week had the same guy in poland on two different days.
I totally agree with the antenna height question, my gainmaster is just about 1.5 metres off the ground and although its getting out ok, itd probably do better with some altitude applied to it, receive on the other hand is a ballache at the minute, local contacts are quieter than dx contacts!
My priority is to get the thing up in the air asap!

Re: linear amplifier

Posted: 23 May 2020, 08:27
by 108EH002
I swapped my sgm from a short pole into the tnk's that are on the side of the house,and put it onto a 19ft pole and it was far better for me in comparison for local/upto 100 mile.

It doesn't really matter if you only want to dx,but I have always seen a big difference when the antenna is above the roofline of the local houses,compared to being on the washing pole 6ft up in the back garden behind the building,especially when someone is static/mobile 50 + miles away (as I am only 400ft asl).

But especially when it comes to the stations that many are trying to make contact with on just groundwave alone.