15 Mar 2014
472kHz ERP over-estimates?
Looking at the reports I send and receive, I wonder if several stations are actually using a LOWER ERP than they think? From measurements I am pretty sure my ERP is 5-10mW with 5mW likely to be the closer figure. Some stations claim 0.5 to 1W ERP which is considerably more than me. Some stations ARE using 6-12dB more than me and to much better antennas but, judging by reports, I should be reporting them much stronger than I do. This could be because (1) my noise floor is worse, (2) my RX is not optimally sensitive, or (3) their ERP is lower than they think. In at least some cases (3) is the reason.
Nearest 474.2kHz report
This afternoon I received a MASSIVE +12dB S/N 474.2kHz WSPR report from G4PZW who is located about 1km (or less) from here. He is in the same QTH square (JO02dg). I met Rob for the first time last weekend at the Burwell Hobbies and Interests Weekend when he was signing GB1BHW, a special event call.
New seasonal DX record on 474.2kHz last night
Last night I received several spots from DL4RAJ at 990km,which is a record, so far this year, for my QRP WSPR signals on 474.2kHz. I am hopeful of better results yet.
My 10mW EIRP maybe be a bit over-estimated as I forgot to divide the measured voltage by 1.414 to convert to RMS from peak. This means my ERP was closer to 5mW, even lower than I had expected, even though I am still showing 10mW ERP on WSPRnet.. This proves, even more, that high power and fancy big antennas are NOT needed to have fun on 474.2kHz MF.
My 10mW EIRP maybe be a bit over-estimated as I forgot to divide the measured voltage by 1.414 to convert to RMS from peak. This means my ERP was closer to 5mW, even lower than I had expected, even though I am still showing 10mW ERP on WSPRnet.. This proves, even more, that high power and fancy big antennas are NOT needed to have fun on 474.2kHz MF.
 |
| 12 unique WSPR spots in last 24 hrs with QRPP on 474.2kHz |
14 Mar 2014
EIRP calculation on 472kHz band
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.
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.
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.
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