So I plugged my measured figures into the equations to work out ERP on the 472kHz band with the very low height Marconi. Measured antenna current is 0.64A and effective height about 1.6m. The formula gives EIRP taking into account the lack of directivity.
EIPR (472kHz) = I^^2 * Heffective^^2 /100 (source LF Today 3rd edition)
= 0.64*0.64*1.6*1.6 / 100 = 10.48mW
ERP is 1.8/2.52 times the above figure, so around 7.5mW.
My estimate of 10mW ERP is a few dB too high, but not a bad estimate, considering experimental error.
As the ERP is proportional to current and effective height both squared, it is easy to see how ERP can be much improved by increased antenna vertical height, increasing the power, or doing both. The other thing is to reduce system losses. An antenna/earth that looks like 300 ohms is probably lossy.
14 Mar 2014
13 Mar 2014
Sputnik days
A message from Oleg RV3GM :
Dear Sputnik'ers
Welcome to "Vanguard-1 QRPp Party 2014"
Dates - March 17 to April 7.
This is not a contest but activity days only. Enjoy milliwatting using old type
Ge transistors TX. See details here -
http://club72.su/vanguard.html
Wish you all the best, 72!
Oleg "Mr. 72" RV3GM / KH6OB
=== In QRP We Trust ===
Very Low Marconi on 472kHz
As from mid-afternoon I am now using a very low height Marconi on 472kHz, tuned against the mains earth (that attaches to a decent ground). The average top horizontal section height is about 1.8m with a horizontal length - a wire along the top of a fence and trellis in an L-shape with a length of around 30m. The whole antenna is just about invisible. The vertical section is just the wire up to the top of the fence.
The whole antenna resonates with a 108uH inductance in series (wound on 110m diam. former) and this is matched to the 12W RF out transverter with a 42mm diameter 3C90 tapped toroid. The antenna looks like 300-400 ohms and the antenna current is 0.64A measured with my current meter. I have ESTIMATED ERP as around 10mW but am probably in a position to calculate this now.
Performance of the very low Marconi compared with the 15m earth-electrode antenna, is about 6-7dB better over probable ground wave paths. So far, the only skywave signal suggests a less noticeable improvement, I think.
The whole antenna resonates with a 108uH inductance in series (wound on 110m diam. former) and this is matched to the 12W RF out transverter with a 42mm diameter 3C90 tapped toroid. The antenna looks like 300-400 ohms and the antenna current is 0.64A measured with my current meter. I have ESTIMATED ERP as around 10mW but am probably in a position to calculate this now.
Performance of the very low Marconi compared with the 15m earth-electrode antenna, is about 6-7dB better over probable ground wave paths. So far, the only skywave signal suggests a less noticeable improvement, I think.
12 Mar 2014
Ofcom and UK Spectrum Sales
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/287994/UK_Spectrum_Strategy_FINAL.pdf
My reading of this OFCOM document is that the UK frequency spectrum is seen as a opportunity for revenue generation. Apparently spectrum "resource" is worth £52 billion to the UK economy. BTW, amateur radio doesn't even get a mention! Radio amateurs do not contribute to this revenue stream and the document does not seem to recognise the self training of radio amateurs in radio science. Maybe they are right: using a black box is hardly skillful or educational.
To my way of thinking, spectrum is a NATURAL resource, a bit like the air we breath or the wind in our faces. Call me an old fashioned socialist (actually this is NOT my natural political stance) but I am uncomfortable that MONEY seems the main, actually the only, motive here.
Give radio amateurs very easy access to "strange" spectrum (e.g. sub 8.3kHz, around 73kHz, and around 40MHz) and access to all licence free slots. Actually, radio amateurs have a lot to contribute and self training in radio science would be ENCOURAGED by such moves.
We are more likely to gain 146-147MHz which, frankly, is a waste: we will gain NOTHING from this except maybe yet more appliance operators using black boxes. 2m is never that busy in my experience. How often are FM channels busy or the SSB slot? Outside contests SSB seems pretty dead on 2m.
We all have a duty to use spectrum wisely, but money is surely not the right way? I am also ANNOYED that so much power and spectrum is in the hands of the UK military. Just look at the current frequency allocations. This is plain wrong in peacetime.
My reading of this OFCOM document is that the UK frequency spectrum is seen as a opportunity for revenue generation. Apparently spectrum "resource" is worth £52 billion to the UK economy. BTW, amateur radio doesn't even get a mention! Radio amateurs do not contribute to this revenue stream and the document does not seem to recognise the self training of radio amateurs in radio science. Maybe they are right: using a black box is hardly skillful or educational.
To my way of thinking, spectrum is a NATURAL resource, a bit like the air we breath or the wind in our faces. Call me an old fashioned socialist (actually this is NOT my natural political stance) but I am uncomfortable that MONEY seems the main, actually the only, motive here.
Give radio amateurs very easy access to "strange" spectrum (e.g. sub 8.3kHz, around 73kHz, and around 40MHz) and access to all licence free slots. Actually, radio amateurs have a lot to contribute and self training in radio science would be ENCOURAGED by such moves.
We are more likely to gain 146-147MHz which, frankly, is a waste: we will gain NOTHING from this except maybe yet more appliance operators using black boxes. 2m is never that busy in my experience. How often are FM channels busy or the SSB slot? Outside contests SSB seems pretty dead on 2m.
We all have a duty to use spectrum wisely, but money is surely not the right way? I am also ANNOYED that so much power and spectrum is in the hands of the UK military. Just look at the current frequency allocations. This is plain wrong in peacetime.
France on MF
Some good news from Andy:
Hello.From to day, 2014 march 12, by publication in the “Journal Officiel” this morning, all french amators may use for transmitting the 472 – 479 kHz segment.73 de Andy F6CNI.
11 Mar 2014
472kHz WSPR update
As of this evening I have received (so far) 12 unique WSPR reports of my 5mW ERP 474.2kHz from the 15m earth-electrode antenna. More spots are very likely in the coming days and nights.
10 Mar 2014
472kHz experiments (continued)
As mentioned in an earlier post, for the last few days I have been using the 15m earth-electrode and not the same antenna with the far end as a capacitive connection to ground as used previously. So far, I have spotted 14 unique stations (best DX DK7FC at 669km) and my own signal has been spotted so far by 10 unique stations (best DX F59706 at 570km) using WSPR.
Overall, my impression is the "proper" earth-electrode antenna is a few dB down, and more directional (?), compared with the similar arrangement but with the capacitive ground connection for the far electrode.
In the coming days I shall extend the baseline and repeat with the capacitive far ground connection. Based on results to date I would expect it to perform quite well, despite what theory might say.
Overall, my impression is the "proper" earth-electrode antenna is a few dB down, and more directional (?), compared with the similar arrangement but with the capacitive ground connection for the far electrode.
In the coming days I shall extend the baseline and repeat with the capacitive far ground connection. Based on results to date I would expect it to perform quite well, despite what theory might say.
Nevada - they clearly don't want my business!
Having asked again for a good deal on the President Lincoln 2 mono-band transceiver for 10m, this was their second reply:
All I can say is others offer a better deal, even without negotiation. Nevada, YOUR loss, sorry.
Had you offered a 2yr warranty and 20 pounds cash discount the sale would have been yours.
Not even discount for a fully upfront cash sale! Clearly this dealer is not interested in my business. A 12 month warranty is also pathetic these days. A 3 yr Square Deal warranty on eBay is only 34 pounds. As a main dealer I was expecting a decent response from Nevada, especially as the similar Anytone rig is over 100 pounds less to buy.Dear Sir,
Thank you for your email. I can confirm that the warranty is 12 months from the date of purchase. Unfortunately however, at this time we are not able to reduce the price but wish you well with your purchase.RegardsHelen WellsNevada
All I can say is others offer a better deal, even without negotiation. Nevada, YOUR loss, sorry.
Had you offered a 2yr warranty and 20 pounds cash discount the sale would have been yours.
President Lincoln 2 - Nevada prices
Today I received a disappointing reply from Nevada:
This is a far worse deal than available from others. I have expressed, to Nevada, my disappointment. At the very least I was expecting a better discount for cash and a much better warranty. I have suggested they reconsider if they want my business. I can wait or go elsewhere.Dear Sir,Thank you for your email. We can confirm that we currently have this radio available for immediate despatch with a total cost (including UK Mainland delivery of 265.90.The warranty period is 12 months from the date of purchase.If we can be of any further assistance, please do not hesitate to contact us.RegardsHelen WellsNevadaUnit 1 & 12 Fitzherbert SpurFarlingtonPortsmouth PO6 1TT
15m earth-electrode
Well, because of my stroke and bad weather, a few days ago was the first chance I had to go into the garden to inspect the far grounded electrode. To my great surprise I discovered my wire was not connected to the ground rod at all and was as my son had left it last September - the wire was just connected to a rolled up piece of coax laying on the ground, in effect a capacitive ground connection: that was why I needed series inductance then! The feed wire is about 1.5m off the ground along a fence. Since the start of the weekend I have been using the far end grounded (as I thought it was originally) to the ground stake. Impedance is still very high (around 200-300 ohms) but I no longer need the series inductance. As for results, it seems perhaps more directional and (maybe) a few dB down on the previous (unintentional) arrangement. Whether the antenna was working as an NVIS wire is not clear but at the old QTH running the wire back through the grass made little or no difference to performance of the earth-electrode antenna, confirming the " loop in the ground" behaviour at MF/LF. I may next try extending the poorly grounded wire further along the fence top to compare performance. The maximum run possible is about 30-35m.
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