1w Vintronics AM rig

[DJMellow]

I brought a 1w Vintronic AM transmitter (FET output).
Im in a flat, and unable to use an external antenna. Obviously AM antennas can be quite sizeable.
Is there anyway of constructing an indoors broadcast antenna?
Potentially I know of some land if worst comes to worst.

Thanks all

[oazz]

https://www.vintronics.co.uk/1-watt-5-1-1-1

[FMEnjoyer]

I think an indoor antenna for AM would be a non starter unfortunately. There are many much more knowledgeable though... I am guessing some exceedingly long dipole as in 2 bits of wire 46M long each would be very good start, one on the + and one on the - ?
Get the wires as high off the ground as you can to give it some chance, easy to say, very difficult to do, also probably quite visible unless literally it's a no go area for some reason. And less face it nowhere is no go here, someone always turns up for dogging, smokes, getting high of gas, nature, extreme sports or some other activity, dodgy or otherwise, even off the beaten track.
Why cannot a little pirate get on without a bunch of reprobates appearing

[radionortheast]

When I had the 4w, using the wire antenna indoors over the light shade, earth connected to the mains, I heard at least very weakly a mile away, sometimes it could not been heard at all, so I suspect the realistic range you’d maybe hear it weakly 500 meters thats about all. The 0.1w ones were very dissapointing nothing heard after 200 meters you do see all those youtube videos people driving around kms away beable to hear them doesn’t happen in reailty.
You can do neutral loading into the mains which might make it get out a bit further, when I did that reception went from been very weak to not been there, to been weak/average, obviously with the power it would be unlikely to get into audio equipment. I didn’t hear the 4w when I tried, I suspect in a flat you’ll share the same mains earth.
I saw a video not so long ago were someone had a wire draped around the side of their bungalow, it didn’t look too unsightly, I guess you'd not be able to do that in a flat, sounded like it worked ok with a range of a few 100 meters with 1w, so similar to those old portable/cordless phones whatever they were in range.
If you have their 4w, you can run it at 12v, thats what I used to do with mine, I guess it was probably less than 4 watt that was been put out there because of that. I tend to think the internals are very similar, they have a higher voltage to the 4w and 8w, I wouldn't recommend any putting a higher voltage through the 1w though to test that theory though.

[EFR]

Magnetic loop works, but go big or go outside.
https://www.66pacific.com/calculators/s ... lator.aspx

[Albert H]

Take a look at the American designs for their LPAM aerials.. Their Part 15 rules insist that the carrier power mustn't exceed 100mW, and the maximum antenna size is 10m. With an optimised system and a really good earth, a friend of mine in Palo Alto in California gets a useable daytime range of about 1 mile with a legal 100mW and shortened aerial. He earths the rig to a metal storm drain that runs for a mile or so down to a nearby river.

Remember - your aerial needs to be as vertical as possible. That being said, we managed to get enormous coverage from just 8 Watts carrier from the top of an East London tower block, using a ¼-wave "sloper" from the top of the block, tied off to a nearby tree at the bottom. Using the building's lightning conductor as a counterpoise, we got very close to a 50Ω match, and the coverage was pretty amazing!

There was an article in Practical Wireless https://worldradiohistory.com/UK/Practi ... 996-07.pdf (Page 37) called "Looping Over The Lawn". This is a design for 1.8 MHz. I've tried a variant of this with more verical than horizontal for the loop at the higher frequency end of the MW band, and got reasonable results, but I was using MUCH more than just 1 Watt!

[radionortheast]

if I remember rightly the lpam stations the ones from hospitals would use alot more power to get the 1w through the antenna, they would look like a huge scanning antenna with 4 rods sticking out the top. It maybe worth looking at top band antennas suppose they could maybe be made to work at a lower frequency.

[jvok]

if I remember rightly the lpam stations the ones from hospitals would use alot more power to get the 1w through the antenna, they would look like a huge scanning antenna with 4 rods sticking out the top. It maybe worth looking at top band antennas suppose they could maybe be made to work at a lower frequency.

Most of the hospital/student LPAMs are/were using Radica gear. Usually the TX, ATU and aerial/ground system came as a package with an Innovonics processor. Aerial was a vertical wire up the inside of a fibreglass mast with a capacitance hat on top. ATU was inside a cabinet at the bottom of the mast to match a coax feedline. TX was 50w dialed in to get 1w radiated, normally needed 30-40w depending on site conditions.

[Albert H]

That's pretty much it. The inefficiency of the shortened antenna is dreadful - it radiates just slightly better than a dummy load!

I did a couple of legal UK LPAM installs. The antenna we came up with used a helical radiator, with guy lines from the top of the radiator. The guys have their first section made from 16 swg sleeved wire, and there;s a further pair of rings of that cable, forming a capacity "hat". The helical nature of the radiator reduces the need for a lossy impedance conversion at the antenna base. We always get as good an earth mat as possible, ideally about an eighth wavelength radius. The transmitter usually needs to run around 17 Watts to get 1 Watt radiated.

My legal RSL / LPAM rig uses an off-air frequency reference, so the PLL is bang on frequency. I used to use 198 kHz as the reference, but since that's no longer reliably available, I've been using the 60 kHz Rugby timecode transmitter which is nearly as frequency accurate as the old Droitwich rig was, The dolts from the DTI came to inspect one installation, and claimed that the rig was off channel by ~85Hz. I showed them that it was actually their frequency counter that was wrong!

We usually provide an Inovonics 222 audio processor (with the European settings, of course), and they always sound great on air. One of the stations had a reliable daytime range in the region of 25 miles to an average car radio!

The restrictions on aerials is ridiculous. Once again, OFCOM do all they can to cripple independant radio.

[radionortheast]

I used to beable to hear york uni before they switched it off, nipped it in the bud, think I heard the hull one years ago to on an evening, before I think they got rid alot of uni stations. I think the tx for york went on ebay a while ago, it was surprised it was much more than 1w, it may of been 50watts, I remembered what I read on here about it. I wonder if anyone bought in the end, they’ve have to have one of those big capacity hats, I suppose that dosen’t mean wearing a top hat and tails lol they've got a nice foot warmer.

It would suprize me if you could get a good signal from rugby, I had a clock it wouldn’t pick up the signal due to interference, maybe abit far away in the north. It was mentioned some were else they’d moved it or lowered the power, maybe clocks could use germany instead? I don’t know. I wonder why the frequency of mains couldn’t be used for a tx, I guess there must be some problem. I once made a clock from the frequency of the mains, it kept the time for all of 45 minutes before it started bouncing around.

[Albert H]

The mains frequency in the UK used to be fairly consistently 50Hz, but since the lunatics took over the asylum and appointed that maniacal zealot Ed Millibrain to Energy Minister, the frequency has gone all over the place as the loading varies and the wind blows or doesn't blow.

Incidentally, that cretin believes that windmills are "green", and that they're magically created from fairydust. He fails to understand that those ridiculous wastes of money will NEVER generate enough power to repay the energy used to mine the materials to make them, make the materials for them, construct them, transport them to site, plant them in the ground (with all that lovely environment destroying concrete), connect and commission them.... Then in seven or eight years, they have to be replaced!

I've got a mains monitor here in my workshop, and over the last three days, the mains frequency went as low as 49.35 Hz, and as high as 50.55 Hz. It averaged 49.877 Hz, so is useless as the timebase for a clock and even worse for the reference for a PLL!

[jvok]

The mains frequency is (or at least used to be) kept stable over the long term, so you get the same number of cycles each day to keep clocks from drifting. But over the short term it can wander a lot as loads changes through the day, so no good for a pll

[Albert H]

It used to be reasonably stable in the UK, and would always average 50 Hz over 24 hours, but that's no longer the case.

In the Netherlands, the mains power frequency (and Voltage) is very stable, but we haven't fallen for the "green" nonsense!

[radionortheast]

I suppose that explains why the clock wouldn't work

[shuffy]

I used to beable to hear york uni before they switched it off, nipped it in the bud, think I heard the hull one years ago to on an evening, before I think they got rid alot of uni stations. I think the tx for york went on ebay a while ago, it was surprised it was much more than 1w, it may of been 50watts, I remembered what I read on here about it. I wonder if anyone bought in the end

I heard that the 1350 setup ended up with a guy in the York electronics department for "disposal". He'd been an undergraduate in the 80s and built one of the transmitters they used with the old "leaky feeder" / induction loop system on 999kHz and for a number of years kept an eye on technical matters at arm's length from URY itself. I don't know if it surprises me or not that they put it on eBay!

[Nige from Brum]

Take a look at the American designs for their LPAM aerials.. Their Part 15 rules insist that the carrier power mustn't exceed 100mW, and the maximum antenna size is 10m. With an optimised system and a really good earth, a friend of mine in Palo Alto in California gets a useable daytime range of about 1 mile with a legal 100mW and shortened aerial. He earths the rig to a metal storm drain that runs for a mile or so down to a nearby river.

It's 100mW DC input to the final amplifier, no 100mW RF and a combined antenna and ground lead length of 3 meters

[Albert H]

I was under the impression that the FCC changed the rules for Part 15 a few years ago, in view of the raised noise floor because of all the noise from Switched-Mode Power Supplies. There were definately changes to the Broadcast Class ratings, with much less nighttime power reduction on AM.

They always rated everything by field strength at a defined distance from the antenna: way back, we got gear impounded because the field strength was so many thousand times that permitted (at the time) under Part 15!.

[jvok]

Its still DC input power for AM. https://www.ecfr.gov/current/title-47/c ... .1.15_1221

§ 15.219 Operation in the band 510-1705 kHz.

(a) The total input power to the final radio frequency stage (exclusive of filament or heater power) shall not exceed 100 milliwatts.

Which is why the US LPAM lot like their class d amps, almost all that DC input goes to the antenna

[DJMellow]

Thank you for all the comments, and help so far. What im going to attempt to do is create some loading coils... guess work a little as I havent got an atu... Finding one online is like a needle in a haystack when it comes to MW. Ive two long whip antennas which can be adjusted, so il run a homemade loading coil into the adjustable dipole, then using field strength on rig should be able to get a rough reading, potentially get it tuned properly