|John Haine||17/01/2019 07:06:47|
|2573 forum posts|
Geoff, if one leg of the loop is an existing fence and the other thin black covered wire in the undergrowth, and it's in the middle of nowhere, it's will be quite hard to spot. And the kind of radios they will use are "clandestine " so I guess they think about things like LO radiation. I have no idea if this is actually used, it was a research project. In WW2 the SOE used Stuart Turner Sirius powered generators run from wood fired boilers, I expect you could see and smell the smoke. Nowadays you'd probably have a solar panel to charge a battery.
My point was simply that you can extract energy by inductive coupling to a power line but it ain't necessarily easy.
Edited By John Haine on 17/01/2019 07:08:04
|Speedy Builder5||17/01/2019 07:17:14|
|1790 forum posts|
Another trick, a cup of water in the microwave, and a filament bulb beside it. Run it at 750watts and the bulb lights up - look, no wires! Hardly "for free" though.
|Robert Atkinson 2||17/01/2019 07:42:19|
308 forum posts
There is such a thing as free electricity (in the UK). As long as you own an electric or plug-in hybrid car and your employer lets you charge it at work. HMRC changed the rues last year and it's no longer a taxable benefit.
|507 forum posts|
Not so free if and when you wish to sell your house. The legalities, etc likely cost the vendor thousands. These rented roofs are a minefield for potential house purchasers. Far better to install your own kit and avoid the third party renters of equipment.
Both my neighbours had the panels fitted by A Shade Greener shortly after I had mine installed & both subsequently sold on. The first had a bit of a gripe from the Halifax BS, but A Shade Greener put an additional clause in the contract that allowed, in the event that HBS re-possesed the house, that ASG would remove the installation without charges if requested to do so - a "backstop" in current parlance, I suppose. Neither my original or new neighbours suggested that this had cost them any extra. With so many of this type of installation (ASG had over 10,000 at the time I saw a TV report about them moving out of their original area into ours & got in touch with them), arrangements will be made to accomodate them when properies get sold.
At the time of installation, the arrangement we have would have cost around £18K so, for me at the time, an outright purchase of my own installation was not possible. Installation costs did come down a lot as numbers of installations increased, so several years later owning my own may have been an option. As it is I generate around 4500 kwh a year, for which ASG receive (IIRC) 42p per kwh FiT & I get to use the electricity FOC - what I can't use at the time it is generated feeds back into the mains.
|Harry Wilkes||17/01/2019 08:27:28|
686 forum posts
It's been suggested two 6" nails will produce free electricity and again so I'm told if your supplier finds out it could result in a stay in one of her majesty's hotels, a room,3 meals a day TV along with other com
|John MC||17/01/2019 08:28:16|
168 forum posts
Absolutely, a real minefield when it comes to house sales and maintenance of the building. Also a number of hidden cost with these rented roof installations, homeowners paying for the cost of scaffolding for the initial installation, costs for an "annual inspection", cleaning costs. There were others I found when researching this. Each installer, it seemed to me, had there own crafty ways of maximising there earnings!
I bought my own installation, for me by far the best option. I worked out that I would get my money back in about 8.5 years, just checked this and am on course for that, if no component failures happen.
I also had an immersion heater controller fitted with the panels at a very good price, in the summer that gives me all the hot water we need at a very, very low cost.
|not done it yet||17/01/2019 08:54:51|
|3144 forum posts|
Too right, JM! mgnbuk might be one of the lucky ones who can use all the energy generated. Many cannot and still have higher building insurance costs as well as all the other tricks the roof renters get up to.
The Solic 200 PV diverters were only about £150 at one time and with simple straightforward installation. Not the best use of high grade energy (unless the property is all-electric) - and solar thermal might be better (if space permits) - but keeps the heating costs down, all the same. There are umpteen instances where the property sells for less, because of the rented roof, or problems when a roof-renter is taken over by another company...
|john fletcher 1||17/01/2019 09:57:46|
|515 forum posts|
Wife and I made our own Solar hot water system more than 35 years ago controlled by a 741 two thermistors and a relay and we installed it all. It worked faultlessly for 26 years, then came along PV panels. Getting older and less agile we decided to have the Solar system removed and have PV system installed. We were one of the first in our area to have panel fitted and we get 52p for every unit generated. and 4p for some thing else. We have a box which allows us to use our immersion heater from the system. Obviously other electrical users must be paying over the odds for their electricity for us to be paid so generously. In 7 years our system has paid for itself and hopefully will continue to do so. John
|Geoff Theasby||17/01/2019 10:05:38|
|587 forum posts|
John, Yes, a solar panel would be the modern way. Tracking the LO would not work with a simple, non-superhet radio, trf, direct conversion, or SDR. The last has a crystal oscillator 'clock' to drive the electronics, but it is very low power, and easily shielded.
|Ian S C||17/01/2019 11:32:43|
7425 forum posts
When I was a kid we built crystal sets, and late 50s got some OC 70 transistors, so made a simple amplifier with a single OC 70, then Dad suggested build another crystal set with broad tuning, instead of the single diode, a bridge made of 4 germanium diodes and an electrolytic capacitor across it, adjust the circuit for the greatest out put, and connect it to the radio. You need 2 good aerials. The main problem with simple radios is the headphones, in general you just can't get high impedance phones.
When I built my first (only) single valve(DAF 91) radio, what to do about HT battery. Built a power supply with a transistor oscilator, feed that through a small low voltage transformer, rectify the HT, and smooth it, and out comes the 90V that I wanted, all from a little 9V battery.
Ian S C
Edited By Ian S C on 17/01/2019 11:45:55
|ronan walsh||17/01/2019 12:13:17|
|539 forum posts|
Yes i did that too, making crystal sets. Ladybird did a little book on it, all the bits held to a piece of pine board (pre-mdf) with brass screws (remember them) and screw cups. I believe pow's made sets using a piece of coke, which was scratched at with a wire until a signal was received.
Kids don't make things like that anymore, they sit gawping at mobile phone screens now.
|4520 forum posts|
I think Andrew misremembers a condition from the old Broadcast Radio Licence. Before TV went big you had to have a Wireless Licence to listen legally to a radio in the UK. Later (about 1970?) this difficult to enforce requirement was dropped. Since then BBC services are funded from the TV licence money and commercial services by advertising (usually).
The 75 foot limit dates to before the War when Regenerative receivers where common. A home aerial would typically be a wire strung from the chimney to a pole at the end of the garden. Regenerative receivers require the operator to achieve selectivity by adjusting an RF amplifier and tuning coil close to oscillation. (It has the effect of improving Q)
Large numbers of people would get this wrong and would have their sets oscillating because real men never read instructions or care about their neighbours! Coupled direct into an end-fed antenna in the garden, the resulting howl could travel several miles. Insisting receive antennas were less than 75 foot long much reduced the nuisance by restricting the wires natural efficiency as a Medium Wave radiator.
Like men with red-flags walking in front of road locomotives the restriction is long obsolete. Superhet radios replaced regenerative types after the war and they are much less likely to couple power into an antenna no matter how gormless the operator. In addition, the Ferrite rods that replaced long wire antennas are grossly inefficient transmitters.
In any case you would either need an enormous antenna and/or be unhealthy close to a broadcaster to leech significant power from the system. Field strength reduces proportional to the cube of distance.
|John Haine||17/01/2019 13:41:51|
|2573 forum posts|
Um, square of distance?
|John Haine||17/01/2019 13:47:15|
|2573 forum posts|
Actually, to be really pedantic, Friis' formula says that the received power is inversely proportional to the (frequency x distance) squared for the far field. If you mean near field then coupled power decreases as inverse 4th or 6th power depending on whether you couple to electric or magnetic field. According to Wikipedia.
|Speedy Builder5||17/01/2019 15:10:07|
|1790 forum posts|
I have my dad's radio licence from about 1920. It allowed him to receive spark transmitted morse code (admiralty Chatham) so long as he did not communicate the contents to anyone else. He went on to Receive 2LO and make home made radios. Things all changed when he finished his dockyard apprenticeship and started as a draughtsman at Short Brothers in Rochester.
|1212 forum posts|
I assume that the subject matter of his work at Shorts was rather different from that at the Dockyard. Was the move from choice or simply the end of his apprenticeship?
There are several period photos of the Shorts factory on the Britain from the Air website:
|4520 forum posts|
Doh, I meant far field, thought square and typed cube. Story of my life!
The gods punish pendants by making them wrong. Always...
|224 forum posts|
I hereby sentence you to be suspended until you acknowledge your errors, pedantically, ad infinitum.
|Speedy Builder5||17/01/2019 21:21:53|
|1790 forum posts|
Ega, Yes, when Dad finished his 7 year apprenticeship, there wasn't a job for him in the dockyard. He bluffed his way into Shorts drawing office on the strength of what he had done at Technical School. The rest is history, but always in aviation finishing up at BAC Weybridge above Barnes Wallaces office.
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.