4 watt MW how far would this go?

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

Post by Zozo » Fri Sep 09, 2022 6:35 pm

fmuser877 wrote: Wed Mar 09, 2022 6:12 pm on the 4 meter cable the signal goes up to 10 and only half on a longer lead yet the FM goes about 2 miles.
You've demonstrated and answered an important factor to yourself regarding the use of a "non" resonate antenna on the 3m band, is going to be drastically different to "non" resonate antenna on say 550m - 200m wavelengths with the same or more power.
Give me a AM transmitter with things that glow any day.

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Re: 4 watt MW how far would this go?

Post by Clutter Free » Fri Jan 13, 2023 2:34 pm

Albert H wrote: 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!
I finally got to lash this antenna together last weekend. WOW!! Amazing results. 30 watts into this antenna was clearly heard 10 miles away, with more tests to come this weekend, and, all with no wire radials on the ground, which keeps her happy :)

Thanks for the heads up on this Albert.

Cheers.

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Re: 4 watt MW how far would this go?

Post by fmuser877 » Fri Jan 13, 2023 5:09 pm

Can you show a pic so can get a rough guess of what to do?
the garden is so muddy so not been to play with AM much.

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Re: 4 watt MW how far would this go?

Post by yellowbeard » Fri Jan 13, 2023 6:50 pm

Here is the Practical Wireless that Albert referred to:
https://worldradiohistory.com/UK/Practi ... 996-07.pdf
You will need to scale the lengths for medium wave, good luck and have fun!

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Re: 4 watt MW how far would this go?

Post by Albert H » Sat Jan 14, 2023 12:01 am

You'll find the article on Page 37 of https://worldradiohistory.com/UK/Practi ... 996-07.pdf
"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 fmuser877 » Thu Jan 26, 2023 11:02 pm

Would this go into a wire to the end of my garden
https://www.ebay.co.uk/itm/282553868063
and boast my signal more?

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Re: 4 watt MW how far would this go?

Post by Albert H » Fri Jan 27, 2023 1:45 am

It might help you to get a match, but "a wire down my garden" isn't going to work too well - most of your RF will be going straight up! You need to get as much vertical antenna as possible. In hard times, I've loaded up an 8m scaffold pole as an antenna, with an area of chicken wire on the ground as a crude "earth mat", and got reasonable results.

The antenna described for 160m in the Practical Wireless "Looping Over The Lawn" article is the way to go! Just scale it up a bit, to bring it down into the MW band, and you'll be pleasantly surprised by how well it can work!

If you can avoid it, don't buy an expensive match box like the one in that Ebay sale - it's easy enough to make your own!
"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 Clutter Free » Sat Jan 28, 2023 9:51 pm

fmuser877 wrote: Fri Jan 13, 2023 5:09 pm Can you show a pic so can get a rough guess of what to do?
the garden is so muddy so not been to play with AM much.
@fmuser877

I will be messing around tomorrow with my set up and I will take a few pics, hopefully, that will aid you to get a bit more coverage from your transmitter.


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Re: 4 watt MW how far would this go?

Post by fmuser877 » Sat Sep 02, 2023 2:56 pm

i AM going to try this aerial
hopefully better than the wire it came with.

https://www.6v6.co.uk/transmitters/torn ... tenna.html

Not really used the tx at all.
if I can get a usable signal I might buy the TX the 15-watt one if get on.

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Re: 4 watt MW how far would this go?

Post by Zozo » Wed Sep 06, 2023 8:09 pm

Thats a lot of monies for a 9:1 unun in a plastic box with some wire. Also what transmitter are you using now? as I recall you had something that is designed for a Hi Z end fed wire and not a 50 ohm system impedance.

You've been given some useful examples from the very start of this thread. Also thinking about throwing more power isn't the answer in your case. You need to choose and install one type of effective compromise antenna that's going to give you the best achievable results for the usable real-estate you have.

Another option is the Inverted L with an L-Match AMU which will give you good results with only 1W of carrier. You'll need at least 50ft of wire. Try 20ft vertically with 30ft horizontally.

The horizontal section can even take a slope towards the ground, but keep the end at least 6ft above ground, and insure using insulators and good quality paracord to support it all.

Finally your need at-least a single earthing rod made from copper pipe buried 3ft into the ground as a minimum, then after some testing you can experiment installing either just one long wire counterpoise laying just on the ground, or multiply wires for a ground plane. Installing additional earthing rods that are electrically bonded to the other ends of the ground plane can have greater effect.

You may wish to look at some other internet resources that will defiantly help you, for example. QRZ Forum, HF Underground and dedicated LPAM groups for part15 hobbyists. Also searching for topics like "best small garden antenna for top band" will give you some additonal food for thought.
Give me a AM transmitter with things that glow any day.

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Re: 4 watt MW how far would this go?

Post by outis » Sun Jan 21, 2024 10:41 pm

fmuser877 wrote: Wed May 19, 2021 3:33 pm Just been looking at this 4 watt MW how far would this go?
they also have 1 watt to

https://www.ebay.co.uk/itm/393314074164 ... 1438.l2649

does it cover just the top band?
A local RSL transmitting on am/mw 1w is clearly heard 6 miles away. 4w would do better.
It will depend on the antenna.

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Re: 4 watt MW how far would this go?

Post by Albert H » Mon Jan 22, 2024 9:39 pm

Zozo wrote: Wed Sep 06, 2023 8:09 pm Finally you need at-least a single earthing rod made from copper pipe buried 3ft into the ground as a minimum, then after some testing you can experiment installing either just one long wire counterpoise laying just on the ground, or multiply wires for a ground plane. Installing additional earthing rods that are electrically bonded to the other ends of the ground plane can have greater effect.
My earth (for many years) is a couple of galvanised dustbins buried about 2m down. It gives plenty of metal surface area underground, and measures well, but freaked out the neighbours when I dug such a deep and wide hole! It's amusing to measure the earth resistance under differing weather conditions. At this time of year, when we have plenty of rain soaking into the garden, the ground impedance is amazingly low, but in the summer it worsens (slightly). It's a really good earth, and much cheaper than buying a whole lot of "proper" ground stakes to bang into the ground!

Just for the sake of amusement, I tried 4 Watts on 666 kHz with 96% mod into my loop, and found that I could easily hear it on my car radio about 15 km away. It was certainly going much further than that, but the experiment was time-constrained that day (I was going abroad that evening).
"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 Zozo » Tue Jan 30, 2024 12:57 pm

Albert H wrote: Mon Jan 22, 2024 9:39 pm
Zozo wrote: Wed Sep 06, 2023 8:09 pm Finally you need at-least a single earthing rod made from copper pipe buried 3ft into the ground as a minimum, then after some testing you can experiment installing either just one long wire counterpoise laying just on the ground, or multiply wires for a ground plane. Installing additional earthing rods that are electrically bonded to the other ends of the ground plane can have greater effect.
My earth (for many years) is a couple of galvanised dustbins buried about 2m down. It gives plenty of metal surface area underground, and measures well, but freaked out the neighbours when I dug such a deep and wide hole! It's amusing to measure the earth resistance under differing weather conditions. At this time of year, when we have plenty of rain soaking into the garden, the ground impedance is amazingly low, but in the summer it worsens (slightly). It's a really good earth, and much cheaper than buying a whole lot of "proper" ground stakes to bang into the ground!

Just for the sake of amusement, I tried 4 Watts on 666 kHz with 96% mod into my loop, and found that I could easily hear it on my car radio about 15 km away. It was certainly going much further than that, but the experiment was time-constrained that day (I was going abroad that evening).
That should provide a very efficient subterranean earthing system at that depth. It’s handy if and when you stumble across old pipe systems to couple onto.

Unfortunately soil conditions at my qth are less than Ideal for an earthing system that deep: I can just about reach 3 feet down before hitting hard bedrock. So over ground counterpoise / radials are my only option.

I certainly see a change in signal propagation during the rainy season, however I have noticed random RF hot spots around the house when the ground is saturated, and completely disappear during dry summer months.
Give me a AM transmitter with things that glow any day.

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Re: 4 watt MW how far would this go?

Post by radionortheast » Thu Feb 22, 2024 2:26 pm

fmuser877 i’ve heard the 4w a few kms away using the neutral, I barely heard anything over a mile away with the wire antenna, indoors, the first experience was a bit disappointing, still quite something i've never had my mw signal go beyond 250meters before, it was only there on some days. I think maybe the fact your antenna is outdoors and you're not getting any better results, may mean you’ve got too many houses round you, not a good earth, a tuning issue, maybe a just the internal inductance setting if it has one. The light display is quite useful, the more lights don't always result in more signal, thats why i'm saying you might want to change the internal inductance and try again.

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Re: 4 watt MW how far would this go?

Post by fmuser877 » Thu Feb 22, 2024 6:27 pm

I put an earth wire around the garden fence but still don't make much difference I don't have any pipes go in the ground I don't think.
yes there houses all around hear too
at least FM can get through them.

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Re: 4 watt MW how far would this go?

Post by radionortheast » Thu Feb 22, 2024 6:58 pm

Looks like you’ve tried everything, yeah fm does work alot better even with low power 1w, when I would often take them on hoilday, with the aerial indoors I could hear them fairly well a mile away allowed me to have some music going. I think its abit hard to measure the signal with mw too, I just about managed it with a little scanner, else theres no idea what the signal is doing, with fm its easy unscrew the antenna you can see you’ve got a good signal with mw you do the same thing and get nothing, so you have unscrew the antenna a bit.

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Re: 4 watt MW how far would this go?

Post by fmuser877 » Thu Feb 22, 2024 9:46 pm

Hopefully there be a DAB modulator some day around 5 to 15 watts that's simple to set up like an FM TX.

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Re: 4 watt MW how far would this go?

Post by Albert H » Fri Feb 23, 2024 4:21 pm

fmuser877 wrote: Thu Feb 22, 2024 9:46 pm Hopefully there be a DAB modulator some day around 5 to 15 watts that's simple to set up like an FM TX.
There already is, but it's a bit too expensive to "lose"!
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