Topics

FDM DUO INCREDIBLY NOISY!!! #fdm-duo

m7mcqio83ro@...
 

Hi all, I just bought a used FDM DUO and when I plugged it in last night at home, it was incredibly noisy!! I thought there was something wrong with my G5RV or with the existing settings in the transceiver, so I performed a DEFAULT RESET and it was just the same.

So a few minutes ago during my work-break I drove up to a high vantage point and connected it up to a LifePO battery. It was nice and quiet.

As soon as I sat back in the car though, it was back to being incredibly noisy with the ignition switched on (but engine not running).  I've had lots of radios and NONE have been noisy like this one. It's soooo poor! 

Are they all like this or have I bought a duffer??

73, Tom. M7MCQ

Klaus Brosche, DK3QN
 

Hello Tom,

Mine is *not* noisy at all.

When yours was nice and quiet on the LiFePo: did you connect any antenna at that point?

In the car: did you feed it there from the LiFePo or from the car battery? Any antenna
connected?

Klaus, DK3QN

Am 05.11.2019 um 14:26 schrieb m7mcqio83ro@...:

Hi all, I just bought a used FDM DUO and when I plugged it in last night at home, it was incredibly noisy!! I thought there was something wrong with my G5RV or with the existing settings in the transceiver, so I performed a DEFAULT RESET and it was just the same.

So a few minutes ago during my work-break I drove up to a high vantage point and connected it up to a LifePO battery. It was nice and quiet.

As soon as I sat back in the car though, it was back to being incredibly noisy with the ignition switched on (but engine not running).  I've had lots of radios and NONE have been noisy like this one. It's soooo poor! 

Are they all like this or have I bought a duffer??

73, Tom. M7MCQ


groups@...
 
Edited

Hello everybody.
Of all my devices: KX-3, Xiegu G90, ALT-512 and FT-891, the ELAD FDM-DUO has the quietest receiver.
With that I can hear the whole evening on my monitor speakers on the shortwave, without it annoying.

Best regards Ralf

Neil Smith G4DBN
 

No they are not like that Tom. I use mine for extreme weak signal work on VHF/UHF/SHF and on LF and it is one of the best performers I have ever used.

Hard to say what is wrong though. The DUO is extremely sensitive compared with many analogue radios, but with the AGC set correctly, it should behave itself unless you are overloading it.

What level in dBm does the display show with no antenna connected and with it connected?

Any sign of the PK indicator showing? If so, does enabling the RX ATT menu 1 make any difference?

If you are not using narrowband antennas, you need to make sure you are not overloading the wideband front end with broadcast signals or anything. If the PK indicator is showing, then you have strong out of band signals that are delivering more than the approx -10dBm total signal that the ADC can handle.  This applies to any SDR of course.

If you are seeing PK overloads, then you need to think about how to reduce the level of the interfering signal.

If the PK indicator is NOT showing, then try these:

Does the noise level change if you connect the antenna, or is it bad even with nothing connected? 

Does it change level if youselect antenna 1 or two on menu 31?

Is anything else connected at all? (keyer, PTT out, ref in, USB etc?)

What settings do you see on tthe E1 control?  Mine has SQL OFF, AGC ON, AGC FAST, AGC TH 3, NR OFF, NB OFF, AN OFF

How about E2? I have RIT OFF, FIL 2700, PITCH 600

I am in USB mode.

See what happens if you adjust the AGC THreshold.

Let us know what you find.

Neil G4DBN


On 05/11/2019 13:26, m7mcqio83ro@... wrote:
Hi all, I just bought a used FDM DUO and when I plugged it in last night at home, it was incredibly noisy!! I thought there was something wrong with my G5RV or with the existing settings in the transceiver, so I performed a DEFAULT RESET and it was just the same.

So a few minutes ago during my work-break I drove up to a high vantage point and connected it up to a LifePO battery. It was nice and quiet.

As soon as I sat back in the car though, it was back to being incredibly noisy with the ignition switched on (but engine not running).  I've had lots of radios and NONE have been noisy like this one. It's soooo poor! 

Are they all like this or have I bought a duffer??

73, Tom. M7MCQ

-- 
Neil
<a href="http://g4dbn.uk/"><small>g4dbn.uk</small></a>

Clint Chron
 

You might want to check your AGC thresh-hold setting.  If it is all way to the right, the radio will be very noisy.  All the way to the left and the radio will be extremely quite.

 

73

Clint

W7KEC

 

From: EladSDR@groups.io [mailto:EladSDR@groups.io] On Behalf Of groups@...
Sent: Tuesday, November 5, 2019 6:51 AM
To: EladSDR@groups.io
Subject: Re: [EladSDR] FDM DUO INCREDIBLY NOISY!!! #fdm-duo

 

[Edited Message Follows]

Hello everybody.
Of all my devices: KX-3, Xiegu G90, ALT-512 and FT-891, the ELAD FDM-DUO has the quietest receiver.
With that I can hear the whole evening on my monitor speakers on the shortwave, without it annoying.

Best regards Ralf

m7mcqio83ro@...
 

Thanks for the replies so far - it's very much appreciated! I will try out some of the suggestions when I get home from work. The FDM DUO was purchased for use in the shack where a Yaesu FT-DX3000 and an Icom IC-7400 perform flawlessly - on the same antenna!

The shack has a fantastic earth system which is just 3 feet away from the rigs. The radio sounds like a noisy old AM transistor set from the sixties, LOL. It's definitely picking up every last bit of noise in the room/area, where the other radios are lovely and quiet.  Again, inside the car (fed from a LifePO battery) the DUO is terribly noisy whereas the other radios are just not affected.

Very odd!! Anyway, I'll try out your suggestions and get back to you tonight. 

THANKS AGAIN for your support.

Tom - M7MCQ

Craig Williams KA6RWL
 

Have you tried your LiPo battery in the shack to rule out noise from your power supply?

I will ditto that of my radios the Duo is very quiet.

Craig
KA6RWL 

David
 

Don’t think I can help as traded in my ICOM 7300 to get an ELAD DUO-ART 120, because I found FDM-DUO’s Rx was much quieter than the 7300’s!

As before, running with no RF ground - my current antennae are five inverted Vees resonant on 40 (and 6), 20, 17, 15 and 10. FDM-DUO is powered from DUO-ART, with DUO-ART and laptop fed from same power socket (via large clip-on ferrite filter- clipped around several turns of mains lead).  Clip-on ferrites on laptop's PSU.  7300  was powered via same filter.

USB leads for FDM-DUO are now as short as possible (50cm), with clip-on ferrites both ends.

Slightly off the thread, an unforeseen plus of the DUO-ART is that its internal ATU tunes my five inverted Vees (all fed unswitched from the same length of coax via a home-made 1:1  current balun) for 60 and 12 metres.  The 7300’s ATU  would not handle that level of mis-match.

David   G8IIC



On 5 Nov 2019, at 15:15, Craig Williams KA6RWL <ka6rwl@...> wrote:

Have you tried your LiPo battery in the shack to rule out noise from your power supply?

I will ditto that of my radios the Duo is very quiet.

Craig
KA6RWL 

m7mcqio83ro@...
 

Okay, so I'm home and have tried the suggestions. Here's the answer to your comprehensive help Neil...

What level in dBm does the display show with no antenna connected and with it connected?
-120dBm

Any sign of the PK indicator showing? If so, does enabling the RX ATT menu 1 make any difference?
NO PK INDICATOR

If the PK indicator is NOT showing, then try these:

Does the noise level change if you connect the antenna, or is it bad even with nothing connected? 
NOISIER WITH ANTENNA CONNECTED

Does it change level if you select antenna 1 or two on menu 31?
THE UNOCCUPIED ANTENNA SOCKET IS QUIET

Is anything else connected at all? (keyer, PTT out, ref in, USB etc?)
NOTHING ELSE CONNECTED. STANDALONE MODE

What settings do you see on the E1 control?  Mine has SQL OFF, AGC ON, AGC FAST, AGC TH 3, NR OFF, NB OFF, AN OFF
SAME EXCEPT AGC TH WAS 0.

How about E2? I have RIT OFF, FIL 2700, PITCH 600
SAME

I am in USB mode.
NOT CONNECTED TO PC YET

===========================================

So the AGC Threshold was at zero which produced more noise. The radio sounds much better - thanks Neil!!

It's still not as quiet as my other radios and has definitely got a higher noise floor than similar SDR radios I've had (FLEX3000 & ELECRAFT KX3). I'll keep on experimenting and see how I can improve things over the weekend.

Tomorrow, my DUO ART 120 with ATU arrives, so maybe the FDM will benefit from drawing its power from the amp? Having said that, I've had zero problems with noise before from my PSU's.

I'll keep you all posted and once again, THANK YOU!!

Tom M7MCQ

Klaus Brosche, DK3QN
 

Tom,

It makes no difference drawing the DUO power from the ART-120, as long as the power supply
to the ART-120 is the same as before (same power source, the DC power feed-through to your
DUO will certainly *not* make your 12 or 13 volts DC power source looking more 'beautiful').

Klaus, DK3QN


Am 05.11.2019 um 20:19 schrieb m7mcqio83ro@...:

Okay, so I'm home and have tried the suggestions. Here's the answer to your comprehensive help Neil...

What level in dBm does the display show with no antenna connected and with it connected?
-120dBm

Any sign of the PK indicator showing? If so, does enabling the RX ATT menu 1 make any difference?
NO PK INDICATOR

If the PK indicator is NOT showing, then try these:

Does the noise level change if you connect the antenna, or is it bad even with nothing connected? 
NOISIER WITH ANTENNA CONNECTED

Does it change level if you select antenna 1 or two on menu 31?
THE UNOCCUPIED ANTENNA SOCKET IS QUIET

Is anything else connected at all? (keyer, PTT out, ref in, USB etc?)
NOTHING ELSE CONNECTED. STANDALONE MODE

What settings do you see on the E1 control?  Mine has SQL OFF, AGC ON, AGC FAST, AGC TH 3, NR OFF, NB OFF, AN OFF
SAME EXCEPT AGC TH WAS 0.

How about E2? I have RIT OFF, FIL 2700, PITCH 600
SAME

I am in USB mode.
NOT CONNECTED TO PC YET

===========================================

So the AGC Threshold was at zero which produced more noise. The radio sounds much better - thanks Neil!!

It's still not as quiet as my other radios and has definitely got a higher noise floor than similar SDR radios I've had (FLEX3000 & ELECRAFT KX3). I'll keep on experimenting and see how I can improve things over the weekend.

Tomorrow, my DUO ART 120 with ATU arrives, so maybe the FDM will benefit from drawing its power from the amp? Having said that, I've had zero problems with noise before from my PSU's.

I'll keep you all posted and once again, THANK YOU!!

Tom M7MCQ


Klaus Brosche, DK3QN
 

Tom,

What also came to my mind:

do you have any sort of non-HAM or HAM transmitter close to your location?

Opposite to your other transceivers, a 'standard' DUO has a wide-open frontend in order
to allow for quite wideband-spread multiple frequency receiving channels.

There is no dedicated per HAM band specific preselection filtering inside the DUO.

Klaus, DK3QN
Friedberg, Bavaria


Am 05.11.2019 um 21:11 schrieb Klaus Brosche, DK3QN:

Tom,

It makes no difference drawing the DUO power from the ART-120, as long as the power supply
to the ART-120 is the same as before (same power source, the DC power feed-through to your
DUO will certainly *not* make your 12 or 13 volts DC power source looking more 'beautiful').

Klaus, DK3QN


Am 05.11.2019 um 20:19 schrieb m7mcqio83ro@...:
Okay, so I'm home and have tried the suggestions. Here's the answer to your comprehensive help Neil...

What level in dBm does the display show with no antenna connected and with it connected?
-120dBm

Any sign of the PK indicator showing? If so, does enabling the RX ATT menu 1 make any difference?
NO PK INDICATOR

If the PK indicator is NOT showing, then try these:

Does the noise level change if you connect the antenna, or is it bad even with nothing connected? 
NOISIER WITH ANTENNA CONNECTED

Does it change level if you select antenna 1 or two on menu 31?
THE UNOCCUPIED ANTENNA SOCKET IS QUIET

Is anything else connected at all? (keyer, PTT out, ref in, USB etc?)
NOTHING ELSE CONNECTED. STANDALONE MODE

What settings do you see on the E1 control?  Mine has SQL OFF, AGC ON, AGC FAST, AGC TH 3, NR OFF, NB OFF, AN OFF
SAME EXCEPT AGC TH WAS 0.

How about E2? I have RIT OFF, FIL 2700, PITCH 600
SAME

I am in USB mode.
NOT CONNECTED TO PC YET

===========================================

So the AGC Threshold was at zero which produced more noise. The radio sounds much better - thanks Neil!!

It's still not as quiet as my other radios and has definitely got a higher noise floor than similar SDR radios I've had (FLEX3000 & ELECRAFT KX3). I'll keep on experimenting and see how I can improve things over the weekend.

Tomorrow, my DUO ART 120 with ATU arrives, so maybe the FDM will benefit from drawing its power from the amp? Having said that, I've had zero problems with noise before from my PSU's.

I'll keep you all posted and once again, THANK YOU!!

Tom M7MCQ



m7mcqio83ro@...
 

Hi Klaus, I have no HAM/CB operators nearby.
As for my shack's  240V, it all runs through one socket which goes through this home-made FILTER.

David Smith
 

You don’t have a Band II (88-108 MHz) transmitter nearby do you? I connected a renowned person-amp to my S2 and Holme Moss 8 miles away caused all sorts of problems 

73 M0OSA 


On 5 Nov 2019, at 21:14, m7mcqio83ro@... wrote:

Hi Klaus, I have no HAM/CB operators nearby.
As for my shack's  240V, it all runs through one socket which goes through this home-made FILTER.

<MainsFilter.jpg>

Thomas McQuiggan <m7mcqio83ro@...>
 

Yes, I live 1 mile away from WINTER HILL transmitter, but it causes me no problems on any other radio.

I ripped out the shack last night to have a big tidy-up, so when it's all back together, I'll do some side-byside comparisons with my IC-7400 and see what happens. The radio is already much better after adjusting the AGC Threshold.

Thanks guys,

Tom - M7MCQ

Neil Smith G4DBN
 

Hi Tom, I live 50km from Emley Moor, and on some bands, the digital TV mixes with cellphone signals from 3km away to make wideband hash which I can only remove by adding very sharp filters.  OK, not on HF, but on there I can't hear much because of VDSL.

Does enabling and disabling the 50MHz low pass filter make any difference?  I had strong medium wave signals nearby, so I fitted an auto-switch filter to my DUO on HF and that removed the crud.  I was seeing a lot of that PK indicator though. Connecting a DUO to a wideband antenna in a high-RF environment is never a great idea, but if the 50MHz LPF makes no difference and the PK indicator is not showing, and if adding more attenuation drops the signal the same amount as the noise, then you are not suffering from overload.

Compare a VERY weak signal on the other radios and the DUO and see if the DUO can hear as well.  You need a signal that is right down at the limit of audibility, ideally a simple tone or CW.  I just hook up my signal generator and put a -130dBm pulsed signal into the antenna as a comparison, then drop the level until I can't hear the pulsing.  It is a bit of a pointless test really, as band noise is way higher than the noise floor of the DUO, but it is a good comparison.  I could be cheeky and say the other radios are deaf of course, that woudl make them quiet!

Try the ultra-weak signal comparison and see what the difference is.

Neil G4DBN

On 07/11/2019 08:57, Thomas McQuiggan wrote:
Yes, I live 1 mile away from WINTER HILL transmitter, but it causes me no problems on any other radio.

I ripped out the shack last night to have a big tidy-up, so when it's all back together, I'll do some side-byside comparisons with my IC-7400 and see what happens. The radio is already much better after adjusting the AGC Threshold.

Thanks guys,

Tom - M7MCQ
-- 
Neil
<a href="http://g4dbn.uk/"><small>g4dbn.uk</small></a>

Klaus Brosche, DK3QN
 

As you might know, FDM-DUO can receive VHF frequencies by means of undersampling.

So as advised already: switch in that RX LPF in Menu #2, if it's not already activated.

Any changes in noise level?

Klaus, DK3QN


Am 07.11.2019 um 09:57 schrieb Thomas McQuiggan:

Yes, I live 1 mile away from WINTER HILL transmitter, but it causes me no problems on any other radio.

I ripped out the shack last night to have a big tidy-up, so when it's all back together, I'll do some side-byside comparisons with my IC-7400 and see what happens. The radio is already much better after adjusting the AGC Threshold.

Thanks guys,

Tom - M7MCQ


Klaus Brosche, DK3QN
 

Winter Hill Transmitter: see here:


OMG! Plenty of 2-digit Kilo-Watts of RF! And just 1 MILE AWAY!

Klaus, DK3QN


Am 07.11.2019 um 09:57 schrieb Thomas McQuiggan:

Yes, I live 1 mile away from WINTER HILL transmitter, but it causes me no problems on any other radio.

I ripped out the shack last night to have a big tidy-up, so when it's all back together, I'll do some side-byside comparisons with my IC-7400 and see what happens. The radio is already much better after adjusting the AGC Threshold.

Thanks guys,

Tom - M7MCQ


Klaus Brosche, DK3QN
 

I was a bit of wrong, sri.

Winter Hill TX is - as can be read - now a dreadful bunch of
100 KW (YES: ONE HUNDRED KILO-WATTS) of multi-channel
UHF transmitters.

Holy cow! What a waste of energy.

Klaus, DK3QN