Tuesday, April 28, 2020

Quarter wave 60m band sloper

Exactly my situation
When in Denmark last year I brought the ARRL antennabook with me to read. It has been given to me by PE1BVQ Hans. A last antenna I wanted to experiment with on 60m is the quarter wave sloper. It is well documented in this book. I know a few others are working with it with very good results. The main advantage is that it is in fact a vertical antenna favouring low radiation angles and some directivity. However:






Find the sloper wire (click for a larger pic)
"You should always remember that it is the ionosphere that controls the elevation angles, not the transmitting antenna. The elevation response of a particular antenna only determines how strong or weak a particular signal is, at whatever angles (or angles) the ionosphere is supporting at that particular instant for that
propagation path and for that frequency"



Not everything is written in this book. I found some other facts as well affecting the performance of the antenna.

- It works extremely well over sea water (as any other vertical)
- It works well over marshy soil
- Very poorly over dry sandy ground
- the properties of the soil will vary from season to season, if you live in an area where there are seasons, of course!
- This means that the performance of classic sloper antennas will range from excellent to mediocre, depending on geographical location and season.

Well, I live on clay ground. It is dry at the moment, but at some seasons it will be very wet. Actually I already imagined better results with the inverted-V in wet weather. I think that wet soil definitely has an effect on the sloper. However, you can't control nature. I wanted to test the sloper against the inverted-V. Switching antennas doesn't reveal much, sometimes the sloper has an advantage, sometimes the inverted-V. I already worked at least one new one on the sloper, CX3CC from Uruquay. So it performs... Receive on the sloper is not as good as on the inverted-V, The sloper is mounted north-west in the direction of the USA and in the direction of the village that always has a slight effect of noise on 60m because of all kind of electrical equipment around the houses.

My test setup
So, I though to do the same experiment as last year with the shunt fed tower. That was a great success but due to new neighbours I could not set it up again since part of the antenna was actually on their property. The sloper is also a test in case I have to remove the inverted-V that is mounted at one side into a tree that is on my neighbour's property.

I made two 5W FT8 stations on 60m and begun to transmit BCN PE4BAS and BCN PE4BAS/P at the same timeslot, hoping that someone would report both my stations in the same timeslot on VK3AMA's hamspots.net, that worked fine last year. But things have changed apparently, old versions of JT-Alert do only spot occasionally to hamspots since it seems to use some kind of random multiserver receiving spots. Besides that once you're spotted you're not getting into the list again for some minutes. Despite multiple transmissions no one seems to spot both stations at the same time slot, strange...I couldn't compare my signal that way.  Another strange thing occured...when someone replied to me both stations PE4BAS and PE4BAS/P were replying at the same time despite 2 different radios, different computers and different antennas. I even used 2 different programs JTDX and WSJT-Z !! I imagine this was very confusing for the opposite station...It is unknown to me what causes this??

So far I could only reliable compare receive signals. I could clearly see a favour to the north and north west. For instance GM6ZAK/QRP was -7dB on the inverted-V and -1dB on the sloper and also other transmissions slots he was most time stronger on the sloper. LA1LO was -3dB and at the same time +11dB (!) on the sloper, a lot of difference. But other signals were weaker especially to the south, French stations were weaker on the sloper and stronger on the inverted-V. Later in the evening I received UN7IT with +1dB on the inverted-V and -5dB on the sloper, but other time slots it was almost a equal signal. Actually I think I should extract some data from the ALL.TXT and make graphs to compare signals over a longer time. On the TX side I could not compare. The only thing interesting was VK7BO receiving my sloper signal with -19dB. I didn't see a report from my inverted-V unfortunately. Tuesdaymorning I was up early to have another try looking for low angle signals which should be present from the USA/West Indies theoretically. It was a disappointment....monitored 2 signals on RX KB1EFS was -5dB on the inverted-V and -7dB on the sloper, 6Y6STAYHOME from Jamaica was -3dB on the inv-V and -13dB on the sloper. However, the noise on the sloper is about 6dB more compared to the inverted-V. The sloper is also fed by about 40m coax which gives about 1,5dB loss were the inverted-V is fed by lossless open line. I did several transmissions on both antennas at the same time and again there was no one reporting the 2 stations at the same timeslot...

For the transmission comparisation experiment I could try WSPR tonight to see any difference, if at least there are some DX stations spotting anyway on 60m. I've been on WSPR 60m years ago but didn't remember what frequency to use. There are 2 WSPR frequencies, one of them is outside our band location. The other one is dail 5364,7kHz which results in 5366,2KHz transmission. Will try that to see what the difference is on TX.

Update Wednesday 29-April:
I set up my 2 WSPR stations transmitting 1W only. Stupid enough I forgot to connect the power supply to the laptop so it switched off at around 01:00 UTC. So unfortunate since I expect most low elevation signals in the morning. However there are some results, TX with 1W in same time slot received by the following random picked station from several directions.

CallBandinverted-V
(PE4BAS)
Sloper
(PE4BAS/P)
OE9GHV60m-8-4
G3ZIL60m-7+3
KD2OM60m-26-24
EA8BFK60m-25-31
G0LUJ60m+1+1
DK6UG60m-2-2
OZ7IT60m+6+6

It is however difficult the transmit all the time in the same timeslot since transmission time is random. So I had to search trough the data. This are the results till the laptop switched off. If you look at it you would say the sloper is better or even with the inverted-V except for EA8BFK, however I've seen other spots from EA8BFK earlier in the evening that were exactly -11/-11 on both antennas. Considering the 1,5dB loss from the coax the sloper is certainly better transmitting till now. N2HQI spotted my "sloper" signal with -27dB, I didn't see any spots from him with my inverted-V signal... However it was raining and the soil was wet, this will increase the performance of the sloper. I will try another night and see if I get similair results. Hopefully I will get a better insight especially in the morning.

6 comments:

  1. Interesting. Can you simply run WSPR receive instead? That way, you are able to check signals simultaneously.

    ReplyDelete
    Replies
    1. John, receive is not always the same as transmit behaviour. I wrote above I have 6dB more noise on the sloper. So I cannot compare signals on receive. And actually in this case I'm more interested in a TX signal comparisation. Receive is good on my inverted-V. Verticals are known for more noise that's why many use separate RX antennas. 73, Bas

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  2. Hello Bas - I was hoping to listen for you on 60m WSPR last night but severe storms forced me to disconnect the antenna. I see you were copied by one NA station...this may not be a good indication of propagation though as very few stations (at least here in US) listen for WSPR on 60m. I will be set up to rx WSPR tonight on 60m.

    73 - John

    ReplyDelete
  3. John, you didn't look good enough. You received my sloper TX signal:
    2020-04-30 03:40 PE4BAS/P 5.366206 -29 0 JO33jk 1 AE5X EM20 8052 298 4
    My inverted-V signal was copied only by KD2OM. My sloper signal was copied by KD2OM, N2HQI, WA2ZKD, K1RA, AF2MP, N8NJ/W, W3PM and AE5X. Just as expected, the sloper clearly transmits low angle signals. The evidence is there. Blogpost will follow. 73, Bas

    ReplyDelete
    Replies
    1. GM Bas - my previous comment refers to the previous night, not last night when I was able to copy you.
      73, John

      Delete
    2. Hi John, the time difference confuses me. Sorry for that. I'm glad you did receive me at least once. Isn't it magical? Just a audio signal from an old Asus mini notebook into an Yaesu FT-817 on 1W into 40m coax which is ending into a steel mast and a piece of copper wire arriving in Texas over a 8000km path. If you told me this 20 years ago....73, Bas

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Thanks for your comment. Bedankt voor je reactie. 73, Bas