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Converting LF/HF amp to HF/VHF ?


Paul Gulliver
 

Chris,

In view of the excellent results Brent is getting with his HF/VHF amp, is there a way the user can convert an LF/HF to a HF/VHF - or is it complete remake.
As you know I've already done the service bulletin 4 mod to my LF/HF model.

Paul


Chris Moulding
 

It's not possible to easily convert a VLF/HF version to a HF/VHF unit.

The reason for the recent Service Bulletin 4 modification was to bring the HF performance of the VLF/HF version up to the same level as the HF/VHF one. Later this week I'll post details of an upgrade kit of parts with a video so that existing customers can add all the upgrades in one session.

One major advantage of the Service Bulletin 4 modification is that it also adds a very effective VHF low pass filter before the amplifier. This helps prevent overload near to VHF/FM, DAB and TV broadcast stations.

Regards,

Chris


Paul Gulliver
 

Ok, thanks Chris

I'm surprised the mod didn't perform better for me as my loop is very similar to the one Brent is using.

Not to worry, will have to look at other options in the future and keep with my MLA-30 for now

Having a look at the possibility of building a M0AYF amp but not sure if its within my capabilities.

Paul


On 02/01/2020 at 10:56, Chris Moulding <chrism@...> wrote:
It's not possible to easily convert a VLF/HF version to a HF/VHF unit.

The reason for the recent Service Bulletin 4 modification was to bring the HF performance of the VLF/HF version up to the same level as the HF/VHF one. Later this week I'll post details of an upgrade kit of parts with a video so that existing customers can add all the upgrades in one session.

One major advantage of the Service Bulletin 4 modification is that it also adds a very effective VHF low pass filter before the amplifier. This helps prevent overload near to VHF/FM, DAB and TV broadcast stations.

Regards,

Chris


leslie norton
 

Have been watching the discussions with interest as i haven’t bought the unit yet.

I did buy a CCW (which is now discontinued) to replace my Wellbrook loop but neither worked for me, I ended up buying a ALA-100 which is a wellbrook loop amp (you supply the wire) Thats worked out very well and i use it on my 190ft Horizontal loop, quite near the ground, which, because of local interference works best for me. I could not null out interference with either the Wellbrook or CCW.

I think performance depends very much on your location.

Also on what you use for your loop, in the UK 1/2 inch soft copper pipe is mega expensive, 10mm is reasonable and pex-al-pex is cheap.

Pex-al-pex makes a really nice solid loop but getting a good connection is difficult.

I do intend to buy one of Chris’s amps but will wait a little while and in the meantime watch with interest.

Les

On 2 Jan 2020, at 10:56, Chris Moulding <chrism@...> wrote:

It's not possible to easily convert a VLF/HF version to a HF/VHF unit.

The reason for the recent Service Bulletin 4 modification was to bring the HF performance of the VLF/HF version up to the same level as the HF/VHF one. Later this week I'll post details of an upgrade kit of parts with a video so that existing customers can add all the upgrades in one session.

One major advantage of the Service Bulletin 4 modification is that it also adds a very effective VHF low pass filter before the amplifier. This helps prevent overload near to VHF/FM, DAB and TV broadcast stations.

Regards,

Chris


Chris Moulding
 

Paul,

I'm back in the workshop and I've just tried the mod you made using the existing toroid core. As you have found it doesn't work very well as the toroid has too much loss.

If you wait until I have the upgrade kits ready I'm sure that you will see the improvement to the VLF/HF versions.

Regards,

Chris

On 2 Jan 2020, at 11:08, Paul Gulliver <paulg1953@...> wrote:

Ok, thanks Chris

I'm surprised the mod didn't perform better for me as my loop is very similar to the one Brent is using.

Not to worry, will have to look at other options in the future and keep with my MLA-30 for now

Having a look at the possibility of building a M0AYF amp but not sure if its within my capabilities.

Paul

On 02/01/2020 at 10:56, Chris Moulding <chrism@...> wrote:
It's not possible to easily convert a VLF/HF version to a HF/VHF unit.

The reason for the recent Service Bulletin 4 modification was to bring the HF performance of the VLF/HF version up to the same level as the HF/VHF one. Later this week I'll post details of an upgrade kit of parts with a video so that existing customers can add all the upgrades in one session.

One major advantage of the Service Bulletin 4 modification is that it also adds a very effective VHF low pass filter before the amplifier. This helps prevent overload near to VHF/FM, DAB and TV broadcast stations.

Regards,

Chris


Paul Gulliver
 

Thanks Chris,

I'll hang on until the upgrade kits

Paul


On 02/01/2020 at 12:18, Chris Moulding <chrism@...> wrote:
Paul,

I'm back in the workshop and I've just tried the mod you made using the existing toroid core. As you have found it doesn't work very well as the toroid has too much loss.

If you wait until I have the upgrade kits ready I'm sure that you will see the improvement to the VLF/HF versions.

Regards,

Chris

On 2 Jan 2020, at 11:08, Paul Gulliver <paulg1953@...> wrote:

Ok, thanks Chris

I'm surprised the mod didn't perform better for me as my loop is very similar to the one Brent is using.

Not to worry, will have to look at other options in the future and keep with my MLA-30 for now

Having a look at the possibility of building a M0AYF amp but not sure if its within my capabilities.

Paul

On 02/01/2020 at 10:56, Chris Moulding <chrism@...> wrote:
It's not possible to easily convert a VLF/HF version to a HF/VHF unit.

The reason for the recent Service Bulletin 4 modification was to bring the HF performance of the VLF/HF version up to the same level as the HF/VHF one. Later this week I'll post details of an upgrade kit of parts with a video so that existing customers can add all the upgrades in one session.

One major advantage of the Service Bulletin 4 modification is that it also adds a very effective VHF low pass filter before the amplifier. This helps prevent overload near to VHF/FM, DAB and TV broadcast stations.

Regards,

Chris



Chris Moulding
 

I've just been doing some more work on the VLF/HF version of the Loop Antenna Amplifier.

It uses a direct coupled amplifier to extend the VLF coverage to less than 10 kHz. I've just modified two VLF/HF head units with a similar transformer to the HF/VHF version apart from the ferrite material. This can upgrade the HF performance but the VLF coverage now only goes down to 50 kHz. I'm currently copying Carribean and W6 Californian stations on 20m FT8 with the 1m coax loop. I can't hear those stations on the main station antenna so it's probably as good or better as the HF/VHF version on HF now.

I'll offer this as an alternative upgrade path.

Regards,

Chris

On 2 Jan 2020, at 13:55, Paul Gulliver <paulg1953@...> wrote:

Thanks Chris,

I'll hang on until the upgrade kits

Paul

On 02/01/2020 at 12:18, Chris Moulding <chrism@...> wrote:
Paul,

I'm back in the workshop and I've just tried the mod you made using the existing toroid core. As you have found it doesn't work very well as the toroid has too much loss.

If you wait until I have the upgrade kits ready I'm sure that you will see the improvement to the VLF/HF versions.

Regards,

Chris

On 2 Jan 2020, at 11:08, Paul Gulliver <paulg1953@...> wrote:

Ok, thanks Chris

I'm surprised the mod didn't perform better for me as my loop is very similar to the one Brent is using.

Not to worry, will have to look at other options in the future and keep with my MLA-30 for now

Having a look at the possibility of building a M0AYF amp but not sure if its within my capabilities.

Paul

On 02/01/2020 at 10:56, Chris Moulding <chrism@...> wrote:
It's not possible to easily convert a VLF/HF version to a HF/VHF unit.

The reason for the recent Service Bulletin 4 modification was to bring the HF performance of the VLF/HF version up to the same level as the HF/VHF one. Later this week I'll post details of an upgrade kit of parts with a video so that existing customers can add all the upgrades in one session.

One major advantage of the Service Bulletin 4 modification is that it also adds a very effective VHF low pass filter before the amplifier. This helps prevent overload near to VHF/FM, DAB and TV broadcast stations.

Regards,

Chris



Paul Sayer
 

Very interesting. I'll wait to see the video to see the upgrade paths. Certainly the first with the cap and inductor look simple enough. Don't know about the transformer mod. I have an older model of the vlf/hf amp.

Paul G0VKT 

On Thu, 2 Jan 2020, 15:00 Chris Moulding, <chrism@...> wrote:
I've just been doing some more work on the VLF/HF version of the Loop Antenna Amplifier.

It uses a direct coupled amplifier to extend the VLF coverage to less than 10 kHz. I've just modified two VLF/HF head units with a similar transformer to the HF/VHF version apart from the ferrite material. This can upgrade the HF performance but the VLF coverage now only goes down to 50 kHz. I'm currently copying Carribean and W6 Californian stations on 20m FT8 with the 1m coax loop. I can't hear those stations on the main station antenna so it's probably as good or better as the HF/VHF version on HF now.

I'll offer this as an alternative upgrade path.

Regards,

Chris

On 2 Jan 2020, at 13:55, Paul Gulliver <paulg1953@...> wrote:

Thanks Chris,

I'll hang on until the upgrade kits

Paul

On 02/01/2020 at 12:18, Chris Moulding <chrism@...> wrote:
Paul,

I'm back in the workshop and I've just tried the mod you made using the existing toroid core. As you have found it doesn't work very well as the toroid has too much loss.

If you wait until I have the upgrade kits ready I'm sure that you will see the improvement to the VLF/HF versions.

Regards,

Chris

On 2 Jan 2020, at 11:08, Paul Gulliver <paulg1953@...> wrote:

Ok, thanks Chris

I'm surprised the mod didn't perform better for me as my loop is very similar to the one Brent is using.

Not to worry, will have to look at other options in the future and keep with my MLA-30 for now

Having a look at the possibility of building a M0AYF amp but not sure if its within my capabilities.

Paul

On 02/01/2020 at 10:56, Chris Moulding <chrism@...> wrote:
It's not possible to easily convert a VLF/HF version to a HF/VHF unit.

The reason for the recent Service Bulletin 4 modification was to bring the HF performance of the VLF/HF version up to the same level as the HF/VHF one. Later this week I'll post details of an upgrade kit of parts with a video so that existing customers can add all the upgrades in one session.

One major advantage of the Service Bulletin 4 modification is that it also adds a very effective VHF low pass filter before the amplifier. This helps prevent overload near to VHF/FM, DAB and TV broadcast stations.

Regards,

Chris



Chris Moulding
 

The transformer mod will be easier to do. We will supply a transformer with 4 wires cut ready to solder to the head unit PCB and stainless steel studs.

Regards,

Chris


Paul Sayer
 

Hello Chris,

How is the update video going for those of us with the original model of the amplifier?

Regards,

Paul G0VKT 

On Thu, 2 Jan 2020, 18:14 Chris Moulding, <chrism@...> wrote:
The transformer mod will be easier to do. We will supply a transformer with 4 wires cut ready to solder to the head unit PCB and stainless steel studs.

Regards,

Chris


Chris Moulding
 

I'd made and edited the most perfect video.

Unfortunately when watching the final version before putting it on YouTube we realised that my hands got in the way of the critical bits of soldering.

I'll remake it today from a different angle.

Regards,

Chris


Paul Sayer
 

A bit of an oops moment!


On Tue, 7 Jan 2020, 08:47 Chris Moulding, <chrism@...> wrote:
I'd made and edited the most perfect video.

Unfortunately when watching the final version before putting it on YouTube we realised that my hands got in the way of the critical bits of soldering.

I'll remake it today from a different angle.

Regards,

Chris