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Audio sound card QRM VHF UHF

 

This type is working very nice as alternative extra sound device for digital modes.
it can work in DVD quality mode as recommended by the WSJT team
But i noticed strong sparking type QRM from it at 144 and even stronger at 432 MHz 
Tried to solve that with ferrite clamps and Aluminium foil without success. 

At 144 i use the IC706 classic no external preamp  25m H2000  12eM2 at 22m ag.  Using no mast amplifier makes my receiving more sensitive for QRM  sources down near the receiver i am aware.
But I keep in mind that the S/N ratio direct at the antenna clamps can only get worse from that point. 
The trade off  is to amplify the antenna signal to a usable level adding lowest possible extra noise .
At the same time keeping the dynamic range and selectivity high enough.
The latest HEM Transistors make this easier then ever before.

And the digital modes of WSJT instantly measure whether an extra pre-amp is really improving the SNR  or not.


Earlier Type1 USB PCB causing less QRM it is recognized by smd tactile switches aft reflow of bad soldered spots this type seems QRM clean 
  


 the device is easy to open with a knife
Then i saw the USB housing shield and other bad joints in solder connections by all 4 USB Sound devices i got, they are very cheap at eBay.
Looks to me that the SMD parts are soldered by machines p & p  and the USB and audio connectors are soldered by hand in a very hasty rough way.
After cleaning and re-flowing  the USB shield was fixed and the spark type QRM seemed gone ..
Unfortunately not i found out after testing at 432.174 MHz FT8
 144 MHz was cleaner but with the microphone cable to the IC451 the old all mode ICOM 70cm there was still a strong sparking QRM  sounding like below at 144 and stronger at 432 MHz
I wonder if any one can confirm this?

sound of the USB QRM

Newer USB Audio Type2 outside appearance is equal causing strong QRM VHF UHF. Its  PCB  differs to type 1. To get rit QRM  i inserted small inductor's in the Audio outputs to the 3.5 connector L/R
C2 and C10 are left out saving mCents?  I will place 1nF  SMD there again maybe that is the easiest way to silence RFI from the chip outputs.


The 0R smd's  are replaced by SMD 6uH inductors that is what i had .  One more had to be done in the picture. There is some headroom under the PCB . Right the mike PCB trace was cut under  SMD choke. Also 3 x 1nF C to ground

Still a good  external ferrite clamp was needed to get the noise floor as low as possible again.  





 


Last week one morning i was shocked  to found a  half Steppir element down on the ground.. 

Seems  it survived the 18m 55' fall but the top part was on the driveway and the postman? drove over it... :-(  
Strong antenna, but the weak spots are the rubber element holding sockets wearing out in a few years and fall apart, Then the element is working its way out of the EHU..
I had checked these sockets months ago there where some cracks i repaired with rubber compound i should have replaced them then ...it seems a matter of time those sockets wear out.. can be dangerous if element fall down like ripe apples.  For a ham like me it is traumatic..


   

Produced by Martens only? offered by  DIY part shops 


Easy to find online,  but  non of the usual DIY markets actual had them although the website showed  like: 3 parts available.

found them here:
 https://www.wesdijk.nl/vijver/vijverartikelen/aansluitmaterialen/rubber-manchet/rubber-verloopsok-50x40mm

Spoiled by eBay Aliexpress  Banggood with low or no shipping costs 
The Steppir parts are available at Steppir USA for reasonable prices but extreem shipping costs 
The complete 18'pole is sold for  65$ but shipping is 70$+ 
in Europe Steppir element 4 part pole is 90€ + 15€ shipping that seems reasonable

But i fixed the top part crushes with epoxy first.

 place extra safety tyraps  parallel over the sockets thanks tip Enno PF5X 

The new socks  heavier quality , the left one caused the element drop damage 4 of the original still hold 



  


 




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