Date   

Re: My SDR-4

martin m3ghe
 

I could've sworn there was an increase in frequency coverage, when it came back it was labelled as a SDR-4+.
My Hi-Z input is still connected to the small wander sockets.   


Re: My SDR-4

Chris Moulding
 

Hi Martin,

The frequency range of any modified receiver would stay the same as the original spec so for your early SDR-4 it is 850 kHz to 40 MHz.

One of the modifications of the early receivers was to replace the original isolation transformer with a new one. This gave better isolation and a flatter frequency range but you lost the high impedance input.

Regards,

Chris


My SDR-4

martin m3ghe
 

Chris, my SDR-4 is serial number 0028.
You had it back a long time a go to modify it.
What was the final frequency coverage and did you remove the isolated antenna input?
Do you have this record? 
I can't find any record my end.

Martin


Re: CCW Inverted-U antenna

David Cutter
 

Thanks for the tip, Adrian.
David G3UNA

On 07 July 2020 at 13:11 Adrian Rawlings <adrianrawlings@gmail.com> wrote:


I finally cracked the 4NEC2 program.

I was despondent when, each time I ran it for the Inverted-U, I got some strange error message.

In the spirit of RTFM, I read the _ReadMeFirst file, and deep inside was an explanation. I'm
running Windows 7.1, and the internal security level was set too high. This is the feature that
sets the degree to which one process and interract with another. I set it to Minimum, and now 4NEC2
works.

I'm posting this message in case someone else has had a similar experience with 4NEC2 and gave up.

To answer my original question, 'What is the radiation pattern like', I can now say 'Complicated,
but OK'. I've taken screen dumps of the

My thanks to Chris Moulding for pointing me in this direction by way of his intial answer.

72 de Adrian


Re: CCW Inverted-U antenna

Adrian Rawlings
 

I finally cracked the 4NEC2 program.

I was despondent when, each time I ran it for the Inverted-U, I got some strange error message.

In the spirit of RTFM, I read the _ReadMeFirst file, and deep inside was an explanation. I'm
running Windows 7.1, and the internal security level was set too high. This is the feature that
sets the degree to which one process and interract with another. I set it to Minimum, and now 4NEC2
works.

I'm posting this message in case someone else has had a similar experience with 4NEC2 and gave up.

To answer my original question, 'What is the radiation pattern like', I can now say 'Complicated,
but OK'. I've taken screen dumps of the

My thanks to Chris Moulding for pointing me in this direction by way of his intial answer.

72 de Adrian


Re: CCW Inverted-U antenna

David Coles M0IDF
 

No problem at all Chris. Very happy to publicise your products. I bought an active loop from you a month or so ago and I love it...in particular:

1) Terrific for indoor use - I was using it with a 1938 TRF receiver last night on 80 mtrs to listen to UK nets. Works brilliantly on Top Band too for fans of 1933 / 1942. I also have a number of vintage domestic wireless sets - Murphys and the like - which are designed for long wire aerials and earths. They're rubbish if you just sling a wire about the room - just pick up a load of noise. Now, if you run a thin coax to the set from the active loop they work brilliantly - because of the loop noise is very low.

2) That deep null. I've messed with passive loops in the past but I have to say the null on yours is the deepest I've encountered. I have VDSL noise from overhead lines to one side nearby and QRM from a neighbour and can use the null to ameliorate the noise considerably. It's also a lot of fun to df signals - broadcast stations and amateurs. Df'ing using the null is far sharper than using the peak.

3) Price - it's a good product at a good price and made in the UK. I'm biased as I grew up just up the road from CCW HQ in Edgworth!

Glad you like the old Hallicrafters S20R. I restore vintage gear for myself and friends. I'd just rebuilt it - new caps, a dozen or so resistors and alignment - it had never been re aligned as all the seals were present - I know it's history and it's an ex VI set from WW2. Brilliant on AM and CW - I take it "portable" with a KW Vanguard! I've got lots of video snippets of me doing things with vintage gear. I should really start a Youtube channel!

I must do a video of me using your active loop too. I might do one on tracking down local QRM as it has the aforementioned very deep null. I'll be ordering one of your multicouplers soon as I have a load of receivers and it's a pain switching aerials.

Best wishes

Dave M0IDF


Re: CCW Inverted-U antenna

Chris Moulding
 

Cracking audio from that Sky Champion!

I hope that you don't mind, Dave, I've run the MOV file through my video editing software and uploaded a smaller 34 MB mp4 file to our web site so that it's easier to find.

The link to the video is:

www.crosscountrywireless.net/IMG_1491_TRIM.mp4

Regards,

Chris


Re: CCW Inverted-U antenna

David Cutter
 

Yes, I did the same and it means learning 4NEC2 which I don't have time for right now. It would be easy if it were in EZNEC which I am familiar with. I assume the issue is the EZNEC doesn't model wires on/near the ground very well.

David G3UNA

On 04 July 2020 at 22:57 Adrian Rawlings <adrianrawlings@gmail.com> wrote:


Chris, thanks for this.

I've downloaded 4NEC2 and the description file for the Inverted U.

I have installed and run 4NEC2 and not got very far. The learning curve, if not steep, seems to be
quite long.

I smiled to myself to see in the Help file the format specification for punched cards. I haven't
used those for five decades, when I was still at school.

So I haven't moved forwards very far.

Looking forward to giving it a try once it's up in the air!

73

Adrian
m0ans

-----------------------------------------------------

From: Chris Moulding chrism@crosscountrywireless.net
Date: 04/07/2020 19:03
Subject: [CrossCountryWireless] CCW Inverted-U antenna
On the web page for the antenna I include the file to use with the 4NEC2 antenna modelling tool.
You can change the antenna mast heights and separation to suit your location and it gives an accurate estimate of how it will work.
Regards,
Chris



Re: CCW Inverted-U antenna

David Coles M0IDF
 

Hi Chaps - I have two friends who each have the inverted U from Chris. They do work very well on 20 mtrs but as you drop down to Top band the efficiency diminishes rapidly. If you look at the model Chris refers to I seem to recall an efficiency of around 1% - Chrsi pls correct me if I'm wrong.

I did play around a lot in the model and Chris's dimensions are the best compromise I found for angle of radiation - you do increase efficiency by increasing the length of the top but it does do weird thing to the radiation pattern.

In spite of the low efficiency on Top Band it does get out on local ground wave. I've attached a video below of me chatting to a chum running about 10 watts around 6 miles away - note mode is AM. He was with another chum who ran around 2 watts of AM from an 817 on battery and I could hear him fine. My antenna is a short loaded inverted L with a raised tuned c/poise.

I set one up at the QTH of a friend. Unfortunately he had horrendous noise levels. The Inverted U did help but it was tough going on Top Band from there. It worked very well on 20mtrs under very flat conditions.

Here's a link to the video - hopefully of interest (Note you don't need to download the video to view. Just click the icon at the lower left and select play)

https://share.icloud.com/photos/0e2L5Fa_11uFK3oqobmfda0rw



Re: CCW Inverted-U antenna

Chris Moulding
 

The NEC2 and NEC4 antenna modelling code is translated from the original FORTRAN code hence the punched card format.

It may be old but the mathematics still work...

Regards,

Chris


Re: CCW Inverted-U antenna

Adrian Rawlings
 

Chris, thanks for this.

I've downloaded 4NEC2 and the description file for the Inverted U.

I have installed and run 4NEC2 and not got very far. The learning curve, if not steep, seems to be
quite long.

I smiled to myself to see in the Help file the format specification for punched cards. I haven't
used those for five decades, when I was still at school.

So I haven't moved forwards very far.

Looking forward to giving it a try once it's up in the air!

73

Adrian
m0ans

-----------------------------------------------------

From: Chris Moulding chrism@crosscountrywireless.net
Date: 04/07/2020 19:03
Subject: [CrossCountryWireless] CCW Inverted-U antenna
On the web page for the antenna I include the file to use with the 4NEC2 antenna modelling tool.
You can change the antenna mast heights and separation to suit your location and it gives an accurate estimate of how it will work.
Regards,
Chris


Re: CCW Inverted-U antenna

Chris Moulding
 

On the web page for the antenna I include the file to use with the 4NEC2 antenna modelling tool.

You can change the antenna mast heights and separation to suit your location and it gives an accurate estimate of how it will work.

Regards,

Chris


Re: CCW Inverted-U antenna

donald sedgebeer
 

On 04 July 2020 at 12:30 Adrian Rawlings <adrianrawlings@gmail.com> wrote:


I have just ordered the balun and 390R resistor unit to make a CCW Inverted-U antenna.

http://www.crosscountrywireless.net/terminated_inverted_u.html

Has anyone experience of them?

Is it at all directional and, if so, in what way?

The design specifies two 10m fishing poles separated by 5m. At the base of one fishing pole there's the 390R resistor pack connected to earth with an earth rod. At the base of the other, there's a 9:1 balun, connected the second earth rod.

Does anyone know if these dimensions are at all critical?

Thanks in advance,

Adrian
m0ans


I have used one for a year or so, The vertical section is a minimum of 5 metre and the top as long as you can get in. mine is 20 metre's It is directional as is all antenna, mine is n/s and fires into the middle east on 14 megs. It must be a current balun. I have had 160 metre contacts on mine. The only answer is try it.
donald


CCW Inverted-U antenna

Adrian Rawlings
 

I have just ordered the balun and 390R resistor unit to make a CCW Inverted-U antenna.

http://www.crosscountrywireless.net/terminated_inverted_u.html

Has anyone experience of them?

Is it at all directional and, if so, in what way?

The design specifies two 10m fishing poles separated by 5m. At the base of one fishing pole there's the 390R resistor pack connected to earth with an earth rod. At the base of the other, there's a 9:1 balun, connected the second earth rod.

Does anyone know if these dimensions are at all critical?

Thanks in advance,

Adrian
m0ans


Re: Loop Antenna Amplifier +

Chris Moulding
 

The big difference in using at horizontal loop is that it will be omni-directional.

It will also receive signals from the ground reflection so at the height it appears to be in the photograph is should be an effective DX antenna at HF.

If the horizontal loop antenna is mounted a few metres above ground lower than 1/4 wavelength at the operating frequency then it makes an excellent NVIS antenna.

The may also be a useful way to reduce pickup of local RF noise.

Regards,

Chris


Re: Loop Antenna Amplifier +

Hisao Uose
 

Hi Chris,

I thought I should test the configuration you've suggested a month ago (a horizontal placement of a smaller loop) before modifying the roll off frequency of "+" head unit. The inter-modulation has almost disappear (faint spurious at 1620kHz detected when operated with 5V but no spurious when operated with 12V). Of course this is a trade off between the gain and the unwanted inter-modulations as you said. I'll do a long term test with other antennas including the CCW VLF/VHF unit paired with 1m copper loop, Wellbrook ALA1530LNP and Apex 303WA-2.

Cheers!

Hisao






On 2020/06/14 2:55, Chris Moulding wrote:
Hisao,

I've run some tests changing the filter capacitors in the Loop Antenna Amplifier + head unit.

Usually the filter capacitors C2, C3 and C4 are 33 pF capacitors. This gives a low pass filter response that rolls off at 150 MHz and is 40 dB down at 220 MHz for the European DAB digital broadcast band.

For your problem with signals at 155 MHz I suggest changing all three capacitors capacitors to 56 pF. This will give a low pass filter response that rolls off at 110 MHz and will be 40 dB down at 162 MHz.

If you still have problems with the 155 MHz signals then try changing C2 to 68 pF. This will give a bit more attenuation at 155 MHz on the input circuit.

Regards,

Chris


Re: loop

Paul Sayer
 

Pex-Al-Pex pipe. 16 or 20mm diameter. About £20 for 25m online or try a plumbers merchant. Light and easy to form. Picture attached of two of mine. I was lucky and mine was free.

Or try an aluminium bicycle wheel as per the video on the website. 

Hope that helps.

Paul G0VKT 

On Wed, 24 Jun 2020, 13:12 chipbutty via groups.io, <stellablade72=googlemail.com@groups.io> wrote:
I got mine from this seller. I'm sure there are many more. Very easy to roll your own. The hard part was drilling a hole in each end.


Re: loop

chipbutty
 

I got mine from this seller. I'm sure there are many more. Very easy to roll your own. The hard part was drilling a hole in each end.


Loop antenna amp +

leslie norton
 

Hi Chris
Did you manage to test the loop amp i sent back for VHF etc?
Thanks
Les


Re: loop

Chris Moulding
 

Hi Gordon,

At VHF the small loop can be a full wave loop. A loop of 1m diameter would be 3.14 m in circumference so would resonate around 95 MHz for FM broadcast listening.

A 800 mm diameter loop would resonate around 120 MHz for airband listening.

A 650 mm  diameter loop would resonate around the 2m amateur band.

Regarding the bias-tee or base unit options, the bias-tee is best if you want the best dynamic range with a good receiver.

The base unit has an extra amplifier which helps poor low sensitivity receivers but may overload good receivers.

Regards,

Chris

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