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My experience so far with the Loop Antenna Amplifier +


Eric Inloes
 

So my amp arrived on saturday and got a chance to do some testing.

Not sure what happened but it seems like it may have been damaged in shipping. I found a bad solder joint with a loose wire for one of toroidal cores that requires me to re-solder to get it functional. Sent some email to you Chris didn't want to send more to bug you. 

I'll be completely honest i'm finding it's HF performance lacking compared to the MLA-30. Right now i am using 1/4 diameter copper pipe. With that said it seems it's VHF performance say for the FM broadcast band is very good and MW is pretty good as well.

Any suggestions here? Perhaps something else is loose as well that could be leading to degraded performance or i'm doing something completely wrong.

Thanks!


Chris Moulding
 

Hi Eric,

In order to answer your question I need a bit more information.

In what way is the performance lacking? Is it lower in level, lower signal to noise, extra noises , overloading the receiver or any other?

If the Loop Antenna Amplifier + is used with the base unit it can have too much gain and can overload sensitive receivers. Having said that I've had feedback from one customer using one with a 1938 TRF receiver with great results.

If it's fed with an internal bias-T in receivers such as the SDRPlay series or the bias-T we can supply the overall gain is around 20 dB lower but it doesn't overload the receiver.

Regards,

Chris


Eric Inloes
 

Hi Chris,

Some more testing may be required I think and I can give much more detail. Earlier this evening I was testing around 5 MHz and was getting a cleaner signal with less QRM vs the other loop amp. Above that seemed to perform worse however with lower signal strength. But with that said static clashes were lower. 

One example of worse performance is WBCQ on 9330 Khz that broadcasts at 500kW was only s9+10 on the CCW amp while it was s9+40 on the MLA-30 amp. I wasn't using SDRuno and it's calibrated S-Meter but i'll try it again. 

With that said at the end of the day S-Units aren't everything. 

Powering with the SDRplay RSPdx and it's Bias-T in this case here using the 10ft 1/4 soft copper pipe bent into a loop.

With that said it's VHF performance again in the FM broadcast band is really good. Weak distant stuff was being pulled in quite well. As a side note I like to do FM Broadcast DXing especially during the peak of the Sporadic-E season and this may replace a dipole for that. 


Chris Moulding
 

Hi Eric,

One point to watch with the MLA-30 is that it does pick up a lot of signal on the coax feeder. This tends to make the nulls from the loop hard to find.

With a loop using the Loop Antenna Amplifier you should have two very deep nulls so check that the station isn't appearing in one of the nulls. You can also use the nulls to reduce local noise and co-channel interference from other stations.

From what you describe it sounds like you had one of the nulls in the direction of the thunderstorms causing the static crashes.

Regards,

Chris


Eric Inloes
 

Hi Chris,

I'd thought i'd post an quick update here before I go. It seems as if the nulls are not as pronounced on the CCW vs the MLA-30 for me for some reason?
 
In this test both loops are inside for testing purposes which isn't ideal but it's a temp solution for testing. 

Here is screenshots of the CCW vs the MLA-30 the loop facing the same direction. On 7325. The higher signal one is the MLA-30. The loops are in the same exact direction. 



Any ideas? 

Thanks for your input!


Chris Moulding
 

Thanks for sending the screen shots, that helps.

There is obviously a difference in level between the antennas of 10 to 15 dB on 7.3 MHz. On the MLA-30 it shows several extra signals that have no trace even at a low level on the LAA+. I've ignored the 40m amateur band as most signals are temporary in nature. It's possible that some signals are spurious on the MLA-30.

This afternoon I've been comparing my sample of the MLA-30 with a LAA+ and another solar powered loop antenna amplifier prototype I've been working on for a few years.

As others have shown in dismantling and measuring the MLA-30 the frequency response is far from flat and my sample appears to peak between 7 to 9 MHz.

The LAA+ has a flat frequency response which explains the difference in performance between the two on medium wave and VHF.

The solar powered prototype is noticeably better than the MLA-30 at it's peak and is also an improvement on the LAA+. The aim of the solar powered amplifier is to feed it with a battery backed solar panel so that the amplifier is fed with very low noise source DC power with enough power coming from the solar panel to keep the battery charged so that the amplifier keeps running overnight and on dark days.

Regards,

Chris


Simon
 

Wow..thats a hard way of doing it! But interesting. ( solar.) what about trying to educate people again about cat 5?

For the gentleman comparing the mla to ccw unit..

See my post on this..do a search..Contentious issue!

The mla is rubbish (IN MY VIEW) ..BUT does have hf gain over ccw..but this is relative..mla has poor noise floor and nulls..( changing the coax helps on the mla.)

I have compared a good few.outcome....ccw for £50 boxed etc is good! One can do better..but £50 for a built ready to go, strong signal handling , good nulls ( i tx 400w VERY close to.) etc is good..
When i say one can do better, i made one..but if i was to sell see £200+.. so..

Ccw unit likes low inductance loop..see mine on posts..10 foot circumference can be reduced to get extra gain on hf without hurting lf bands.( again see my pics of my loop.)

Just to add..no lf band ham dxers use mla’s..none..all use lz1aq..wellbrook or ccw..( or homebrew.) or other rx antennas..flag, beverage etc..

Also..position of loop relative to buildings/noise is very important..
Try moving loops..
Also as you state you have mla and ccw same direction close this may not be a fair comparison..
I say this as the mla receives more omnidirectional than the ccw due to coax pickup..
Try changing direction of ccw unit..null out the station of interest, then rotate 90 and compare again.. just as a test??

Sorry for jumping in!!! (probably should stay quiet!!)

Mag loop Simon g0zen

Stay well!


Tom Crosbie G6PZZ
 

Eric,

I think what’s more important is that you identify exactly what these higher level signals are. It could, after all be spurious signals generated in the RX. The frequency range you’ve chosen is a bit weird, to me anyway. Some separation and identification of those signals would prove beyond a doubt if they are genuine signals or not.

 

The giveaway is that the MLA gain isn’t constant across the frequency range. You’ll note the rise in noise level above 7.6MHz. In the CCW trace, the gain is more consistent across the range.

 

Indoors is not the best location for testing antennas, surrounded by electrical noise from household appliances and wiring. You are not being fair to either antenna.

 

73 Tom G6PZZ

Nr Chesterfield | NE Derbyshire | UK | IO93he

HF250 | Sentinel 4 | RSPdx | RM50 | TR2 | ATS 808

15m MLB | MTA | D707

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Eric Inloes
Sent: 17 August 2020 12:25
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] My experience so far with the Loop Antenna Amplifier +

 

Hi Chris,

I'd thought i'd post an quick update here before I go. It seems as if the nulls are not as pronounced on the CCW vs the MLA-30 for me for some reason?
 
In this test both loops are inside for testing purposes which isn't ideal but it's a temp solution for testing. 

Here is screenshots of the CCW vs the MLA-30 the loop facing the same direction. On 7325. The higher signal one is the MLA-30. The loops are in the same exact direction. 



Any ideas? 

Thanks for your input!


Eric Inloes
 

Thanks for the suggestions.

I'll try to get outside and try again and try to make screenshots a little bit more clear. I normally use SDRconsole but use SDRuno in this case for it's calibrated S-Units. 

Tested mediumwave more closely and it yielded higher SNR using in general it appears so some interesting results. 


Roger Need
 

On Mon, Aug 17, 2020 at 04:25 AM, Eric Inloes wrote:
In this test both loops are inside for testing purposes which isn't ideal but it's a temp solution for testing. 

Here is screenshots of the CCW vs the MLA-30 the loop facing the same direction. On 7325. The higher signal one is the MLA-30. The loops are in the same exact direction. 



Any ideas? 

Thanks for your input!
Your noise floor in those screenshots  is way too high!  So you either have a LOT of noise,  the RF gain in SDRuno too low or your Auto IF AGC is off.  You should have Auto IF AGC on and you should increase the RF Gain to just below the point where A/D overload comes on.

Roger (SDRplay beta tester)


Eric Inloes
 
Edited

Here is some more screenshots if it helps on 15 Mhz from earlier today comparing the two amps. The MLA-30 is the one with much more noise. Both lops were sitting on my patio during this. 

Should I zoom in more instead? Not sure if that is more helpful then a wideband view. 

I am in a urban area so my HF noise floor isn't the best in the world. 



Thanks :)


Eric Inloes
 
Edited

Also, I just noticed now that it appears i'm getting FM broadcast images at various spots in the HF spectrum. It's not horrible or all over just some spots. Could this be causing desensitization?

Thanks 


Roger Need
 

Just so you know SDR-Console does not have a calibrated S-meter / dBm readout like SDRuno.  The numbers mean nothing because as you change IF and RF gain and sample rate the readings change.

Best to stick with SDRuno if you want meaningful comparisons.

Roger


Eric Inloes
 
Edited

Hi,

Thanks for the heads up on that. Why I try to use SDRuno for power levels but i'm way more accustomed to SDR Console esp with it's gain control etc.

With that said getting some nice results on Mediumwave and 5 Mhz besides the FM broadcast images at various places. Loop inductance in play here? Perhaps it's still too high with 1/4 copper pipe. Seems nulls are working for Mediumwave. Not sure what can be done to fix the broadcast FM images. 

There is a 15kW and a 20kW around 30 miles or 48km away but they both come in very strong here on dipoles. Those seem to be coming in at random places and hear them switching to a Broadcast FM demod. From my location of the loop almost a clear line of sight path with no obstructions. 

There is another 20kW station around 8 miles or 13 KM away but not causing issues for whatever reason. It's on low part of the FM band at 88.1 MHz.

I can't fully filter this band out as I actually plan to use the band from time to time for DXing since i was quite impressed that i could pull in weak signals well with the loop and null stuff out a bit. 

Any more ideas? 

Thanks :)


Simon
 

Yes you can filter it out..

Switchable..so when fm band  dxing switch it out..otherwise in..


Mag loop simon

On 18 Aug 2020, at 12:34, Eric Inloes <compaq963@...> wrote:



[Edited Message Follows]

Hi,

Thanks for the heads up on that. Why I try to use SDRuno for power levels but i'm way more accustomed to SDR Console esp with it's gain control etc.

With that said getting some nice results on Mediumwave and 5 Mhz besides the FM broadcast images at various places. Loop inductance in play here? Perhaps it's still too high with 1/4 copper pipe. Seems nulls are working for Mediumwave. Not sure what can be done to fix the broadcast FM images. 

There is a 15kW and a 20kW around 30 miles or 48km away but they both come in very strong here on dipoles. Those seem to be coming in at random places and hear them switching to a Broadcast FM demod. From my location of the loop almost a clear line of sight path with no obstructions. 

There is another 20kW station around 8 miles or 13 KM away but not causing issues for whatever reason. It's on low part of the FM band at 88.1 MHz.

I can't fully filter this band out as I actually plan to use the band from time to time for DXing since i was quite impressed that i could pull in weak signals well with the loop and null stuff out a bit. 

Any more ideas? 

Thanks :)


Tom Crosbie G6PZZ
 

Hi Eric,

My suggestion to the VHF/FM problem would be to install the antenna outside and at the receiver end use a VHF bandstop filter.

 

You haven’t mentioned the RX in use, or I’ve forgotten! I have an RSPdx which has three inputs. I would use a two way switch with the antenna connected to the common, with a straight coax from one output to one of the RX inputs. The other output I would use to install the bandstop filter inline to one of my other inputs. This gives you the option of switching from one to the other.  

 

Coax switches are expensive, so I’ve attached a document I wrote some time ago that was uploaded to another group. This shows how to construct a simple switch for very little outlay. Ignore the last couple of lines until Chris says I can upload things! My antennas and layout have also changed.

 

Have fun but stay safe

 

73 Tom G6PZZ

Nr Chesterfield | NE Derbyshire | UK | IO93he

HF250 | Sentinel 4 | RSPdx | RM50 | TR2 | ATS 808

15m MLB | MTA | D707

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Eric Inloes
Sent: 18 August 2020 12:30
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] My experience so far with the Loop Antenna Amplifier +

 

[Edited Message Follows]

Hi,

Thanks for the heads up on that. Why I try to use SDRuno for power levels but i'm way more accustomed to SDR Console esp with it's gain control etc.

With that said getting some nice results on Mediumwave and 5 Mhz besides the FM broadcast images at various places. Loop inductance in play here? Perhaps it's still too high with 1/4 copper pipe. Seems nulls are working for Mediumwave. Not sure what can be done to fix the broadcast FM images. 

There is a 15kW and a 20kW around 30 miles or 48km away but they both come in very strong here on dipoles. Those seem to be coming in at random places and hear them switching to a Broadcast FM demod. From my location of the loop almost a clear line of sight path with no obstructions. 

There is another 20kW station around 8 miles or 13 KM away but not causing issues for whatever reason. It's on low part of the FM band at 88.1 MHz.

I can't fully filter this band out as I actually plan to use the band from time to time for DXing since i was quite impressed that i could pull in weak signals well with the loop and null stuff out a bit. 

Any more ideas? 

Thanks :)


Eric Inloes
 

Hi Tom,

I am using the SDRplay RSPdx here.

Seems using the FMBC bandstop filter built into the SDR itself doesn't do much so perhaps it's form the loop amp itself?