4 watt MW how far would this go?

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fmuser877
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4 watt MW how far would this go?

Post by fmuser877 » 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?

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Re: 4 watt MW how far would this go?

Post by Zozo » Wed May 19, 2021 4:14 pm

For an example go to this website http://www.mediumwaveradio.com/lpam.php and find a 1W LPAM Station near to you. Then either by car or on foot, see how well the signals propagate.

It's also worth noting that these stations use a specific type of compromise antenna. If your able to install something bigger, then all the better.

Type of antenna used by UK LPAM Stations https://radica.com/services/low-power-am

The TX you've linked to covers the top part of the Medium Wave Band. Which is ideal for LPAM Stations .

I've previously listed the LPAM frequencies before on this thread viewtopic.php?f=11&t=2868
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Re: 4 watt MW how far would this go?

Post by fmuser877 » Wed May 19, 2021 6:00 pm

bbc local is turning off hear but its bottom band but would be nice to have something replace these.

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Re: 4 watt MW how far would this go?

Post by Zozo » Wed May 19, 2021 6:38 pm

OK that TX is not going to be much use, as it's lowest operating frequency is 1024Khz.

The higher part of the band is normally used for LPAM because the types of compromise antenna's work very well there.

You should perhaps consider this https://www.ebay.co.uk/itm/AM-MW-RADIO- ... 4546506500

Or this: https://www.ebay.co.uk/itm/AM-MW-RADIO- ... 4546500832

Either will require you to install them in a suitable housing / box. Lower frequencies will require a much larger antenna than what's used for traditional LPAM stations, but there are a few options available.
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Re: 4 watt MW how far would this go?

Post by fmuser877 » Wed May 19, 2021 7:00 pm

oh so this why the shorter cable prob be better to go top end.

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Re: 4 watt MW how far would this go?

Post by Zozo » Wed May 19, 2021 7:12 pm

Here's just some food for thought. But the best type of antenna that I use regularly in the upper regen of the MW band is the "Vertical Monopole". This is basically just an end fed wire or aluminum tube at a maximum height of 32 feet.

You also require ground radials too. which can be omitted, but performance is drastically reduced if you do choose not to use them.

At the base of the antenna is a loading coil to overcome the reduced length of the radiating element. At higher frequencies this coil is usually not all that large in inductance.

You can further reduced the loading coil size by either, increasing the diameter or the radiating element, or adding a capacitive hat at the top.

These antenna's work well, and I've been using them for many years on numerous bands. i.e. MF and HF frequencies.

Here's an example of the vertical monopole with ground radials.
LPAM.png
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Re: 4 watt MW how far would this go?

Post by Zozo » Wed May 19, 2021 7:14 pm

Here's a good fiberglass telescopic pole. https://www.ebay.co.uk/itm/122295664458
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Re: 4 watt MW how far would this go?

Post by Zozo » Wed May 19, 2021 7:22 pm

If you do decided to use this type of antenna which is very similar to the commercial type available, all-be-it minus the capacitive hat. The loading inductance @ the lower end of the band will be very large.

Example of inductance required using a 30 foot 1mm wire driven element.
30F-Vertical-Monopole.png
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Re: 4 watt MW how far would this go?

Post by Albert H » Wed May 19, 2021 9:54 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 too

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

Does it cover just the top band?
It just covers the top end of the band, which is where the shortened "compromise" aerials tend to work best. Your question about how far it will travel is really dependent on antenna efficiency and how good an earth you can provide. We used to operate a station with 8 Watts carrier / 32 Watts peak, into a sloping quarterwave wire, and could cover most of London (weakly) in the daytime. At night, it was completely flattened by big signals from Europe, so we only operated in the daytime. We chose a frequency that was clear in the daytime, and were pleasantly surprised by just how far our (relatively) low power signal could go.

Back in the early 70s, I ran a station in the Netherlands that used a single 807 valve for about 18 Watts carrier / 65 Watts peak (using an old valved guitar amplifier as the modulator!). The antenna was a "Marconi" type, and in the daytime we covered much of the Benelux with a reasonable signal - certainly receivable on the usual kid's transistor portable!

One thing I learned from my early experiments was that modulation depth was everything - the mod had to be consistently LOUD! To achieve that, I built a compressor. I also found that high treble content was wasteful because the receivers wouldn't reproduce it, so I built audio lowpass filters to cut off everything over 6kHz, and apply a bit of boost from 3kHz upwards to make the signal sound less "muddy".
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Re: 4 watt MW how far would this go?

Post by Albert H » Tue May 25, 2021 3:37 am

Further to the above:
I ran a 5 Watt carrier / 20 Watt peak rig into a "shortened" vertical last week. It was perfectly receivable (daytime) 30 km from the site on my car radio.

It appears that OFCOM aren't too bothered about Medium Wave. As long as you don't cause interference, you'll probably go unnoticed for a long time! Bearing in mind that MW gear is cheap and easy to build, and that cheap CMOS logic can make a perfectly viable synthesiser allowing accurate frequency generation without specific crystals, I'd suggest that a few of you should give it a go. The most expensive part of the whole thing will be the wire for your aerial!
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Re: 4 watt MW how far would this go?

Post by Zozo » Tue May 25, 2021 12:00 pm

Good coverage Albert. I'm still able to compete to a certain degree with one high powered European station at night. But obviously I'm not covering anywhere near the same area I was during the daytime.

Using a portable radio with the ferrite rod antenna gives me slightly better results, as I'm able to turn the radio into a null spot for the European station.

I'm currently only using 30 radials spread out evenly for my earthing system. I have experimented with more, but I found no significant improvement to my signal. It could possible be soil conditions helping in that area.

I may change that wire to either tinned copper or stainless steel, as I've noticed a couple of connections have gone green and very brittle using pure copper.

Be nice to see others at-least try some experimenting with AM Broadcasting.
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Re: 4 watt MW how far would this go?

Post by teckniqs » Tue May 25, 2021 1:45 pm

In Manchester there is or was a LPMW station on 1580AM (I think it was) called Range Radio coming from Whalley Range School, and at just 1w ERP you can still receive it a good 5 miles away on a portable radio.

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Re: 4 watt MW how far would this go?

Post by Zozo » Tue May 25, 2021 10:28 pm

Possibly 1584 Khz. Might not have been LTRSL on that frequency, but I wouldn't know for sure. It's not listed now.

LTRSL http://static.ofcom.org.uk/static/radio ... m-list.htm

Not listed on the Analogue: FM & AM list either.

http://static.ofcom.org.uk/static/radio ... e-main.htm

Thinking though it could have been a Special Event or RSL licence??
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Re: 4 watt MW how far would this go?

Post by teckniqs » Wed May 26, 2021 3:53 am

I've tried a quick Google search for it and it doesn't look like it's around any more but it was on for whole 4 years I lived around there from 2007-2011.

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Re: 4 watt MW how far would this go?

Post by reverend » Wed May 26, 2021 9:45 am

Some years ago, before LPAM was a thing, I was involved in a university radio station. We had a 1 Watt (carrier, 4W PEP) AM transmitter and used an antenna strung between the roof of two buildings (it was supposed to feed a series of loops underneath the campus, but these had fallen into disrepair). I would say we managed to cover about 2 miles in most directions. The station later moved onto an official 1 Watt LPAM transmitter and coverage was very similar.
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Re: 4 watt MW how far would this go?

Post by Albert H » Thu May 27, 2021 1:32 am

Since we're pirates, we're not limited to the "official" inefficient aerials!

The "tower block sloper" was (effectively) an inverted-V aerial, using a quarter-wavelength wire diagonally off the top of the block as the "hot" side, and using the building's lightning conductor as the other side. A quick check with an Antenna Noise Bridge showed that the impedance at the frequency we chose was about 50Ω. We used 20 Watts carrier / 80 Watts peak (at most), and a couple of the rigs were phase-locked to Droitwich 198kHz to guarantee their frequency accuracy!

We used cheap HEXFET devices for the output (and the modulator), and the best FET of all (that I found at the time) was the 2SK135. It's in a TO3 case, and the source is connected to the case, obviating the need for any insulation. These devices would work up into the short wave bands, and (at the time) it was a cheap part. These days I'd look at more modern (and therefore more efficient) switching FETs.

The most expensive part of the whole system will be the wire!
"Why is my rig humming?"
"Because it doesn't know the words!"
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