4 watt MW how far would this go?

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fmuser877
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Re: 4 watt MW how far would this go?

Post by fmuser877 » Wed Mar 09, 2022 6:40 pm

Is the aerial on the back a very low power and is that the better one to connect the longer wire to?
https://pbs.twimg.com/media/FNbakWzXwAQ ... ame=medium

fmuser877
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Re: 4 watt MW how far would this go?

Post by fmuser877 » Wed Mar 09, 2022 6:41 pm

I read what the knobs each do to.

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Re: 4 watt MW how far would this go?

Post by yellowbeard » Wed Mar 09, 2022 10:13 pm

That's not an antenna - :o . You are going to need either a resonant antenna or the longest, highest length of wire you can put up, a decent earth and a antenna tuner to make it resonant at your frequency. A 1/4 wave down that end of the band is 150-175 feet long, serious real estate is needed. For a more modest but less efficient setup, have a look at this PDF:
https://sites.google.com/site/lowpowerr ... y-antennas
It has a few types of antenna you could lash up in an afternoon for not much money, and details of tuners. These designs are for LPAM operators in the USA, they are limited to a 10 foot radiator - but if you can put up 30 or 40 feet all the better, it will affect the range of the tuner required though. Also you can never have too much metal buried in the ground for an earth, a grounding rod is a bare minimum.

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Re: 4 watt MW how far would this go?

Post by fmuser877 » Mon Apr 04, 2022 3:56 pm

So my dad bought home this copper the other day can I reuse this to increase the range thanks

https://pbs.twimg.com/media/FPgZEOLXoAQ ... name=large
https://pbs.twimg.com/media/FPgZEmtXwAA ... name=large
https://pbs.twimg.com/media/FPgZFD3WUA8 ... name=large
https://pbs.twimg.com/media/FPgZFoHX0AQ ... name=large

at the mo, it's just running off the dipole at the end.

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Re: 4 watt MW how far would this go?

Post by Albert H » Tue Apr 05, 2022 12:17 am

One MW installation I've done recently uses a loop aerial - 9m up, 16m across the garden, 9m down and a return at (just above) head height back to the starting point. The part of the vertical near to the house is RG8 coax, and the rig feeds the inner, with the rest of the loop connected to the outer - basically making a long, thin transformer! It matches at about 18Ω, and the rig output stage is dimensioned to match into this directly. Radiation efficiency is surprisingly good, and for a peak DC input power of about 140 Watts, (suggesting a carrier power of around 30 Watts with the kind of efficiency I normally get out of Class E stages), I got daytime coverage that would be the envy of many FM stations!

The antenna design was suggested in a Practical Wireless article "Looping Over The Lawn", back in the '80s. In that case, it was used for "Top Band" - 160m / 1.8 MHz. I was pleasantly surprised how easy it was to get some radiation from this makeshift aerial, and experimenting with a chicken-wire groundplane didn't significantly add to the radiation.

The rig itself is a very simple CMOS synthesiser driving a couple of paralleled FETs for the PA, and modulated by (effectively) a power Op-Amp (LM3886). The most expensive parts of the rig are the mains transformer, the 19" rack box it's built in, and the heatsinks!
"Why is my rig humming?"
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Re: 4 watt MW how far would this go?

Post by stretchyman » Wed Apr 06, 2022 5:07 pm

I've had reports of strong signals upto 5 miles using a base loaded 8' vertical with minimal grounding from a US customer with sporadic 100 mile DX at night. The unit he was using is my MiNi Tx and will give 20W carrier at 24V and 5W at 12V. Way better than any other TX on the market! Class E RF and class D (PWM) modulator.

Other models available..

Str.

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Re: 4 watt MW how far would this go?

Post by yellowbeard » Wed Apr 06, 2022 7:54 pm

Albert H wrote: Tue Apr 05, 2022 12:17 am The antenna design was suggested in a Practical Wireless article "Looping Over The Lawn", back in the '80s. In that case, it was used for "Top Band" - 160m / 1.8 MHz. I was pleasantly surprised how easy it was to get some radiation from this makeshift aerial, and experimenting with a chicken-wire groundplane didn't significantly add to the radiation.
I spent an hour looking for that article, turns out it was 1996 :lol: Page 37 in this file:
https://worldradiohistory.com/UK/Practi ... 996-07.pdf

In fairness it would have taken me 10 minutes to find it, but I kept stopping to look at what bits J.Birkett had on offer.

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Re: 4 watt MW how far would this go?

Post by Albert H » Thu Apr 07, 2022 1:29 am

[quote=yellowbeard post_id=36189 time=1649271251 user_id=1072

I spent an hour looking for that article, turns out it was 1996 :lol: Page 37 in this file:
https://worldradiohistory.com/UK/Practi ... 996-07.pdf
[/quote]

You're right, of course! (My aging memory.....)

The use of a length of coax as the coupling transformer makes construction quite easy. The one I've lashed up here this afternoon has the coax in a 8" diameter coil, and the series capacitor is made up of a few fixed silvered mica caps in parallel with a 150p compression trimmer in parallel for the final tweak. The mess I lashed up matches 50Ω pretty well. I plan to put a few watts into it tomorrow.

If anyone's interested in MW, you can get pretty good rigs from "Stretchyman", and it's not too difficult to build your own with a handful of CMOS for the synthesiser, a couple of FETs for the output, and an audio "power op-amp" (like the TDA2040 or the LM1875) for the modulator. It won't be the most efficient in terms of power consumption, but it's cheap!
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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Re: 4 watt MW how far would this go?

Post by stretchyman » Thu Apr 07, 2022 8:45 am

Thanks for the Flowers Albert!

I use a DDS which if programmable via a usb adapter or a costed down version that uses a CPP oscillator from Cardinal for single channel use. Same RF and Mod.

I'm going to try the loop over lawn jobbi and compare to vert.

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Re: 4 watt MW how far would this go?

Post by Albert H » Thu Apr 07, 2022 10:25 pm

My experiment this afternoon gave quite remarkable results. My little AM rig delivers 32W carrier and peaks at around 130 Watts at full mod. The frequency I chose was 1125kHz, and I fed it first with 1 kHz tone, and later with some arbitrary stream from the interweb. A few phone calls revealed reception at 18 miles, 33 miles and (weakly) at just under 50 miles. Driving around showed that the aerial was reasonably omni-directional, though there was a null in the direction of the house. I think that it's a success!

Incidentally, the rig is a somewhat unusual out-phased type, with a pair of Class D PAs feeding the output coupling. The modulator uses a couple of comparators (working out-of-phase), and the carrier is a CMOS-synthesised pseudo-sinewave which is filtered to smooth it enough to feed the modulator. Te whole mess is in a small diecast box, and barely gets warm (unless the antenna match is bad!).
Last edited by Albert H on Thu Apr 07, 2022 10:32 pm, edited 1 time in total.
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"Because it doesn't know the words!"
;)

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Re: 4 watt MW how far would this go?

Post by Albert H » Thu Apr 07, 2022 10:27 pm

Incidently, a friend of mine has a "Stretchyman" SW rig (on 6.3 MHz) and it works well. The build quality is fine, and the overall efficiency is very good. If you're looking for something pre-built, he provides good solutions.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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Re: 4 watt MW how far would this go?

Post by sinus trouble » Sat Apr 09, 2022 11:19 pm

yellowbeard wrote: Wed Apr 06, 2022 7:54 pm I spent an hour looking for that article, turns out it was 1996 :lol: Page 37 in this file:
https://worldradiohistory.com/UK/Practi ... 996-07.pdf

In fairness it would have taken me 10 minutes to find it, but I kept stopping to look at what bits J.Birkett had on offer.
Once again YB!! You are an absolute Ledge!! :lol:

That Magazine archive you found has kept me busy all week, Also brought back some great memories! :D

The Maplin Magazines have been a real blast from the past for me! :lol:
I am as stupid as I look! :|

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Re: 4 watt MW how far would this go?

Post by sinus trouble » Sat Apr 09, 2022 11:22 pm

Dodgey Radio Character.PNG
:lol:
You do not have the required permissions to view the files attached to this post.
I am as stupid as I look! :|

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Re: 4 watt MW how far would this go?

Post by stretchyman » Tue Apr 19, 2022 1:00 pm

The eternal question!

However 4W carrier (16W pep) will with a decent antenna will get out 4 miles or so. Just transmitting into a piece of wire however long generally won't work at all, ever.

I get asked this question ALL the time only seconded by, 'Do you sell antennas'.

Look, if you want a decent range, firstly purchase a product that has a 50R connector on the rear. Anything with 'It transmits into a piece of wire connector' is going to be crap.

Secondly spend time making a decent resonant antenna and for MW a base loaded vertical as tall as poss, whilst not be the most efficient (5%) will give good range.

Any antenna can be checked with a NANOVNA, worth buying and learning how to use.

Did I say..... I sell transmitters?

Str.

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Re: 4 watt MW how far would this go?

Post by Medley2k » Tue Apr 19, 2022 6:05 pm

sinus trouble wrote: Sat Apr 09, 2022 11:19 pm
yellowbeard wrote: Wed Apr 06, 2022 7:54 pm I spent an hour looking for that article, turns out it was 1996 :lol: Page 37 in this file:
https://worldradiohistory.com/UK/Practi ... 996-07.pdf

In fairness it would have taken me 10 minutes to find it, but I kept stopping to look at what bits J.Birkett had on offer.
Once again YB!! You are an absolute Ledge!! :lol:

That Magazine archive you found has kept me busy all week, Also brought back some great memories! :D

The Maplin Magazines have been a real blast from the past for me! :lol:
I had forgotten all about the Maplin magazine. What a legend YB! Thanks for posting up a link to this archive.

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Re: 4 watt MW how far would this go?

Post by Clutter Free » Tue Apr 19, 2022 10:53 pm

stretchyman wrote: Tue Apr 19, 2022 1:00 pm

Did I say..... I sell transmitters?

Str.
I see you have abandoned eBay Stretchyman. Is it a PM job now if a TX is required?

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Re: 4 watt MW how far would this go?

Post by stretchyman » Fri May 20, 2022 7:55 am

Why not email me?

[email protected]

Would be fine!

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Re: 4 watt MW how far would this go?

Post by radionortheast » Wed Jun 29, 2022 9:28 am

Hi fmuser887, I don't know how technically minded you are but you might want to try connecting to the neutral, its called neutral loading i've found it works better than any antenna wire you can rig up around the house. You just need a spare plug lead socket to do it and a high voltage capacitor, I use 68pf 1000volt. I connect to the antenna at the back, using terminal block to the neutral, using the high voltage capacitor, I then connect blue wire, then you just connect the earth from the mains to that of transmitter, the green wire. I'm assuming your transmitter is the same as mine, I have the 4watt version, it has inbuilt atu its important you won't be-able to tune it other wise, all you have to do is tune it, it should at least make it possible to hear the signal a little further than before.

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Re: 4 watt MW how far would this go?

Post by fmuser877 » Wed Jun 29, 2022 3:21 pm

I will also try making the wire go higher the highest point is the tv aerial so will see if can get a wire over that
and back down to the end of the garden I have not really played with it much more.

as the 7w FM one from the bottom floor can cover over 1 mile OK

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Re: 4 watt MW how far would this go?

Post by radionortheast » Thu Jun 30, 2022 10:24 am

FM is much easier to do, if your not borthering anyone I can’t see any harm in it. I don’t think many people listen to fm here now, or they have it tuned to one station, all the choice is on dab and online, think soon even big companies will just do online radio, it will unviable to transmit on fm, it will be people with an interest in broadcasting who will be left!.
It was just a novelty hearing my signal coming throught on mw I liked, its always been a place for boring waffle oldies stations noone listens too so to have some more modern music coming throught was quite good! some Paloma Faith! The only good thing was you don’t get interference from in car transmitters, I do worry about interupting someones stuff, theres so many of them going past here all the time.
I’ve never beable to get a signal go beyond 250 meters on medium wave, those 0.1w transmitters are no good for anything, except for someone sending their signal 2 feet away to an antique radio. My transmitters just been left under the bed since, I can’t see much use for it, you get a lot of noise in the backround, humming, suppose it is quite funny to hear. With fm I get a clear signal 1km away it depends were the car is parked up the road on half a watt into an indoor aerial, you won’t get any stereo with that, it is still better than am. I did a lot of listening on AM before, i’ve not found any unlicenced signals there, there are quite few dutch unlicenced stations you can hear on a night above 1600khz.

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