The purpose of this article is to show direction to individuals on methodology to minimize the RX noise reduction in the Quadra VP-1000 and VL-1000 combination by Yaesu. Most of the ham equipment available can use these basic concepts and no originality is claimed.
My area of interest is weak signal/digital modes on the 6m amateur band; so when after doing due diligence/research on the Quadra I was disappointed when it arrived due to a sudden increase in RX noise floor reception when first switched on.
Research has shown that the Quadra is a fully matured product which first came out into manufacture in 1997 just pre the digital age in ham radio. PSK by Peter G3PLX wasn't released to the wider ham community till 1998.
Consequently what was leading edge/best practice back then, doesn't apply in some areas now.
When the Quadra was first hooked up and evaluated, he following was observed on the companion FT-950......
the noise floor rose.
when the VP-1000 cooling fans kicked in, a wide band noise pulse was audible and showed up on the Spectrum Laboratory waterfall.
there seemed to be a very low residual tone all the time while in the USB RX mode.
The next day I decided to take off the covers and see what Yaesu had and more to the point not done due to cost restraints. First impression was that the Quadra is a well made product and still is for that matter.
The manufacturer has recognized that noise exists and has a filter module [ filter-unit br001480a ] internally in the VP-1000 end and at the VL-1000 end tubular ferrite's in the 8 pin Molex Control socket line at the VL-1000 end (very likely added to meet CE EMC criteria. - Ed.)
After poking around inside I decided to put the covers back on with the view of using a home made piece of coax cable with a 2 turn link on the end to DF the external noise egress. I found the following ....
the biggest noise source was radiation emanating from the black 8-core Control cable connecting the VP-1000 to VL-1000.
low noise on the CT-118 cable to the FT-950.
residual on 50 volt dc cable.
residual on outer of coax to input of VL-1000 from FT-950.
Hmmmm: what to do next ????
The next day after a good sleep and armed with ideas I used tried and true passive techniques, firstly ....
A: 3 and 4 mm stainless shake proof washers placed under any screws that could be easily got at to improve positive earthing; that includes the coax connectors as well! also the screws that hold the PCB's to the mounting pillars.
NOTE : Yaesu (and for that matter most other manufacturers) have nice black shiny outer cases painted on both sides with questionable electrical contact via the screws. (The VL-1000 and VP-1000 cases are unpainted on the inside. - Ed.)
B: placed snap-on ferrites inside the VP-1000 at load side of 15A mains circuit breaker (those two white wires) at the input / output JP1001 and JP1003 CONTROL filter module br01480a.
The purpose of the above is to keep the genie inside bottled up; once it exits via the connectors/cables it is a much harder task to eliminate.
snap-on ferrite on CT-118 at the VL-1000 end.
snap-on ferrite on input 2 coax cable at VL-1000 end from FT-950.
snap-on ferrite on both ends of 50 volt dc patch cord.
snap-on ferrites at both ends of black control cable. Since this CONTROL cable radiates most profusely I have enclosed it in aluminum kitchen cooking foil as well. This is wrapped around it, earthing this doesn't seem to make any difference but certainly contains the EMI.
snap-on ferrite to 6m Yagi aerial to output 1 to kill noise traveling down on braid to Quadra / FT-950.
TAKE NOTE: There is no magic bullet that allows one to place a snap-on ferrite at position xyz to solve this problem. Yaesu went to a lot of trouble in 1997 to solve it back then but most likely had to give up due to cost restraints. It is a case of what you are happy to accept and leave it at that. My setup is extremely quiet.
THE PROBE MADE FROM COAX CABLE AND A 2-TURN LINK IS YOUR BEST FRIEND. (This probe can be used in conjunction with a spectrum analyser as a powerful "EMC sniffing" tool. - Ed.)
Peter VK6KXW 15/11/2009
Here is a follow-up on my previous EMI noise article. I have done more work on this.
I decided during the VK winter period to revisit the Quadra with a view of what could be achieved internally.
My noise probe (coax with 1 turn loop) indicated that the main culprits where the fascia display board and controller board with its inter-connection loom. The EMI being emitted was very substantial; this in turn was being conducted by common mode along all the white control wires to the rear of the Quadra and ultimately into the coax sockets.
Hmmmm: what to do?
I firstly tried ferrites but could not achieve sufficient impedance as the wires are drum-tight and could only get about 200 ohms for one pass through a snap-on ferrite. I slept on this discovery overnight and woke up the next morning with the memory of an article by Jim Brown K9YC on twisting wires.
After a tentative try on the easy bundles, I immediately had positive results. Then, over a 2 day period, I twisted the white control wires going hither and thither and dressed all coax cables/looms for best practice.
The results were impressive using Spectrum lab and the noise probe. However, there was still some residual EMI coming off the big display board on to the controller board, so I came up with the idea of a big plate on metal stand-off pillars with the connecting control wires twisted and coming out of a grommet.
The Quadra is now EMI quiet - far quieter than factory spec, which is already pretty good.
Peter VK6KXW 20/10/2010
Copyright © 2009 - 2010 Peter Jackson VK6KXW. All rights reserved. Last updated: 20/10/2010.
Text edited and this page created by A. Farson VA7OJ/AB4OJ.