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Bias T unit polarity

richard@...
 

Which is the positive on  the LAA++ Bias T unit cable please? Centre or outer?
Re: inverted U antenna #chat

Chris Moulding
 

Due to restricted access to the workshop at the start of the Covid lockdown we stopped making all products except the LAA++ and the HF/VHF/UHF Multicoupler.

We are gradually bringing some of the products back but have had to stop due to the demand for LAA++ and HF Multicouplers caused by customers monitoring the battlefield HF traffic from Ukraine.

The plan is to bring the 9:1 balun and resistor unit for TIU antennas next with the Broadband Active Antenna soon after that.

Regards,

Chris
Re: inverted U antenna #chat

dgw007
 

Hi Chris,  can I ask why you stopped production of the inverted V antenna? I have found mine to be very good,   with the Wellbrook no longer used.

Its been up for quite a few years now ,  had no issues, but wondering what I would replace it with if that time comes. 

On Tue, 20 Sept 2022, 10:32 Chris Moulding, <chrism@...> wrote:
Hi Martin,

Good to hear that the TIU is working well for you.

Regarding antenna patterns, on the web page is a file that can be opened in the antenna modelling program 4NEC2.

You can then change the mast heights and spacing to suit your location and run the program to check the antenna pattern at different frequencies.

For my own ham station I'm experimenting with NVIS antennas so the Mk2 is likely yo be a NVIS version.

Regards,

Chris

Re: inverted U antenna #chat

martin.porter@...
 

Thanks Simon! Just need to find out how to modify it now - but thanks again.

-----Original Message-----
From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Simon
Sent: 20 September 2022 18:06
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] inverted U antenna #chat

If memory serves me..
4nec2 is free, download install On pc.
Download Chris’s file, open in 4nec2
Job done.
Re: inverted U antenna #chat

Simon
 

If memory serves me..
4nec2 is free, download install On pc.
Download Chris’s file, open in 4nec2
Job done.
Re: inverted U antenna #chat

Martin - M7MNP
 

Thanks Chris..

Is there a paper on how I can get the data into 4NEC2 or has someone got the Nec source file I can play around with?

 

Thanks

Martin M7MNP

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Chris Moulding
Sent: 20 September 2022 10:33
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] inverted U antenna #chat

 

Hi Martin,

Good to hear that the TIU is working well for you.

Regarding antenna patterns, on the web page is a file that can be opened in the antenna modelling program 4NEC2.

You can then change the mast heights and spacing to suit your location and run the program to check the antenna pattern at different frequencies.

For my own ham station I'm experimenting with NVIS antennas so the Mk2 is likely yo be a NVIS version.

Regards,

Chris

Re: URM67

Martin - G8JNJ
 

On Sun, Sep 18, 2022 at 06:49 PM, Chris Moulding wrote:
The best one is the simple 1m diameter loop. This gives the lowest inductance and will cover the HF bands up to 30 MHz.
I agree with Chris, screened and Moebius loops simply aren't worth the effort, and rarely provide any of the advantages that are claimed of them.

https://www.g8jnj.net/moebius-loop-antenna

Notes regarding broadband loop inductance.

https://www.g8jnj.net/loop-inductance

If you are connecting loops in parallel, there seems to be an optimum value of spacing, which is somewhere around 1 loop radius.





Regards,

Martin
Re: inverted U antenna #chat

Chris Moulding
 

Hi Martin,

Good to hear that the TIU is working well for you.

Regarding antenna patterns, on the web page is a file that can be opened in the antenna modelling program 4NEC2.

You can then change the mast heights and spacing to suit your location and run the program to check the antenna pattern at different frequencies.

For my own ham station I'm experimenting with NVIS antennas so the Mk2 is likely yo be a NVIS version.

Regards,

Chris
Re: URM67

richard@...
 

Cheers Chris.
inverted U antenna #chat

Martin - M7MNP
 

Hi Chris / everyone! 

Chris - had your inverted U up and running now for well over a year now, and It's still cracking - I'm just wondering if you have a radiation pattern you can share? 

I have it on two 12m poles and about 15m spacing between them. I have also extend the earth lead by another 6m at each end with extra earthing rods. This has taken the noise 
level below S2, S3-4 on a bad night (With my old HF Vertical,  that was around s9 on a good night!) 

If you ever get around to doing a Mk2 of the Inverted U - I'll be the first in line to buy it! 
thanks Chris

Kind regards
Martin M7MNP.
Re: URM67

Chris Moulding
 

I've tried probably all the loop configurations that could be used with the LAA++.

The best one is the simple 1m diameter loop. This gives the lowest inductance and will cover the HF bands up to 30 MHz.

If you want to use the LAA++ with the loop to monitor VHF airband then you can reduce the circumference of the loop to 2.5m so that it is a full wave loop at 125 MHz. This will still work well at HF.

If you want to use the extra coax try making a double loop similar to the military HF loops. That consists of two identical 1m diameter loops about 100mm (4 inches) apart connected together at the ends to connect to the amplifier terminals. This will reduce the inductance of the loop allowing more RF current to flow and will give a similar result to using copper pipe without the extra expense or plumbing skills needed.

Regards,

Chris
URM67

richard@...
 

I've got an LAA++ arriving next week and have ~8 metres of URM67 coax to make a loop with. 

Should I just make a 1 meter diameter loop or is there a configuration that will allow me to use all of it?
Re: LAA++ coax for loop?

Paul Newland
 

Sorry about that Ruchard, however, if you look back for Chris’s previous response to really the same request a couple of conversations ago on this group.
Best of luck going forward
Paul

On Sun, 11 Sep 2022 at 10:45, <richard@...> wrote:
Hi Paul

Thanks for the reply but the link leads to my Gmail account rather than this group.

Richard

--
Best Wishes
Paul
Re: LAA++ coax for loop?

richard@...
 

Hi Paul

Thanks for the reply but the link leads to my Gmail account rather than this group.

Richard
Re: LAA++ coax for loop?

paul newland
 

Hello Richard
May I suggest that you have a look at a previous conversation on this group that I believe may be helpful to you,
The link below is to Chris's las comment on it and if I recall correctly this was previously recommended by him for not least it's ease of forming a loop - but have a look yourself.
https://mail.google.com/mail/u/0/#trash/FMfcgzGqPzPFDKVsPZvRpCqjxddjqSPC
Best wishes
Paul
LAA++ coax for loop?

richard@...
 

Hi all. First post.

I'm thinking of buying an LAA++. If I make a loop out of coax is the quailty of the coax important or does it not matter?

Richard
Re: [resolved ]Re: High Z Antenna Amplifier - intermods

Chris Moulding
 

Hi Nick,

Interesting to hear about your additional common mode filter.

The common mode filter built into the amplifier has around 50 uH inductance from memory.

Your additional choke will certainly stop any noise on LW and MW.

Regards,

Chris
Re: Coax recommendation

Chris Moulding
 

I used the LDF 4-50A coax to make a test loop.

I used a 3 m length of it to make a loop just under 1 m diameter.

There is a photo of the test loop on the Loop Antenna Amplifier web page.

Regards,

Chris
Re: Coax recommendation

John Buckley
 

Hi Chris,
I've just purchased a Loop Antenna Amplifier ++ from you and so far have made a very basic loop. 
You mention LDF4-50 , well , I have some Cellflex LCF 12-50 which appears to be the RFS equivalent .
Can you suggest or point me to some designs for using it in a loop antenna build please.

Regards,
John  2E1JBC

On Tue, 23 Aug 2022 at 21:15, Chris Moulding <chrism@...> wrote:
For HF receive use with the High Z, Loop and Beverage amplifiers the coax losses are relatively low even for long runs so other factors such as cost, lifetime or ease of installation become major factors.

Most of the amplifiers are set up for 50 ohm output but it's a simple resistor change during build to give the option of 50, 75 or 100 ohm output impedance.

In actual receiver use the mismatch between 50 and 75 ohm coax is barely noticeable so 75 ohm CCTV cable is a good option.

Our earlier active antennas used CAT5 ethernet cable using one pair as a 100 ohm transmission line, two pairs for DC power with one pair spare. We did manufacture a cross polarised active antenna that used the spare pair as an additional RF transmission line to go with the dual diversity SDR receiver we made some years ago.

The only reason we stopped selling antennas using CAT5 cable was that our professional customers didn't want to replace their existing coax cable runs with CAT5.

What do I use myself? Both at home and in the workshop I use coax cable runs of RG-58u with runs up to 25 m long. It"s mainly due to the ease of installation and the fact we always keep a drum of it in stock to make connecting cables.

By the way in my previous professional life designing and installing coverage enhancer systems for mobile phone networks we only ever used Andrews LDF 4-50 cable. This would be well over the top for HF receive use but it's great for making HF loops!

Regards,

Chris
Regards,

Chris
Re: [resolved ]Re: High Z Antenna Amplifier - intermods

Chris Moulding
 

Hi Nick,

Interesting to hear about your additional common mode filter.

The common mode filter built into the amplifier has around 50 uH inductance from memory.

Your additional choke will certainly stop any noise on LW and MW.

Regards,

Chris
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