Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Removing Alternator whine from transmit on TYT Chinese 2m /70cm mobile?  (Read 577 times)
KT0DD
Member

Posts: 450




Ignore
« on: June 15, 2019, 09:06:00 AM »

Hi all, I have alternator whine getting into my cheap Chinese dual band mobile. Yes, probably a lack of filtering from China I know, so don't bash me for being cheap...Hi - Hi. Anyway, are there any simple fixes like a capacitor across the power wires, or do I need to find an alternator whine kit of some sort? (haven't seen many of these since the CB craze died out years ago. Constructive help is appreciated.

73. Todd - KT0DD
Logged
K5LXP
Member

Posts: 6092


WWW

Ignore
« Reply #1 on: June 15, 2019, 11:25:19 AM »


Sometimes it's how the radio is powered.  If the negative lead is grounded somewhere other than the lowest ground impedance point (usually where the battery grounds to the frame) there can be ripple currents that go through the radio chassis and can be heard as alternator whine.  So before you go through extraordinary measures with filtering, the chassis connection should be verified.

Another test to do is if it's still present when connected to a dummy load.  This can also reveal currents going where they shouldn't, in this case through the coax shield.

Next I'd verify the ripple under load.  This will show if it's a radio problem, or a vehicle problem.  If you have a bad rectifier or regulator in the alternator that's the thing to fix, not the radio power.

Mark K5LXP
Albuquerque, NM
 
Logged
KX4QP
Member

Posts: 364




Ignore
« Reply #2 on: June 16, 2019, 04:59:20 AM »

If you haven't (and can), you might also check the alternator on a scope.  Alternators are multiphase (usually three, but I've heard of higher phase counts) AC generators with internal full wave rectifiers.  The output has considerable ripple when independent of the battery (it'll be the sum of the three rectified phases).  However, it's moderately common for one diode in the rectifier to fail as a short (or get bypassed by dirt), which will permit (partial voltage of) one phase to get through as AC.

Since this is added to the rectified voltage from the other phases, it will show mainly as a drop in voltage at one sixth of the ripple frequency.  This failure can lead to whine that gets past normal filtering (because the amplitude is much higher than the usual ripple); it can also kill your battery over time (especially if it actually manifests as a negative voltage, even for a short spike).  Batteries don't like AC; in a lead acid type, it can cause the electrolyte to drop far faster than normal (we used to say it was "boiling dry").

New alternators are somewhat expensive, but they're fairly easy to replace, at least in older cars (haven't tried it in anything made in the past almost-thirty years).  It used to be possible to replace the rectifier in the alternator, as a less costly alternative, but I doubt that's the case in modern cars.
Logged
W4JCK
Member

Posts: 148




Ignore
« Reply #3 on: June 17, 2019, 08:15:28 AM »


Sometimes it's how the radio is powered.  If the negative lead is grounded somewhere other than the lowest ground impedance point (usually where the battery grounds to the frame) there can be ripple currents that go through the radio chassis and can be heard as alternator whine.  So before you go through extraordinary measures with filtering, the chassis connection should be verified.

Mark K5LXP
Albuquerque, NM
 

Exactly.  Most notorious is the cigarette lighter jack.  Chinese radio or not, I've heard so many radios over the years on the repeaters whining away due to being powered through that source.  Sometimes you can connect at the fuse block and solve it - other times not - a cable run to the battery is required.  As Mark said, it will depend on how your grounding and chassis bonding is implemented.

Good luck
Logged
KL7CW
Member

Posts: 555




Ignore
« Reply #4 on: June 17, 2019, 12:35:34 PM »

Since your post title says whine on TX, and if there is no whine on your RX, I think it is probable that the whine is coming into the radio power and/or grounding scheme, not the antenna.  A very easy test is to temporarily power your radio with a separate battery from another vehicle, lawn tractor, or even possibly a string of D cells if it is a low power rig.  If the whine goes away, as suggested separate ground and power wires to the battery may fix the problem.  Often a simple 12 volt feed through capacitor made for automobiles will give you many dB of whine attenuation, which may be enough if the whine is not too strong on your transmitted signal.  These capacitors typically were in a metal case with a bracket with a hole, which you could attach to a grounded metal surface either with a bolt or perhaps a sheet metal screw.  Probably these caps are available at an auto stereo shop, or 2 way radio shop, or on line from an electronics supplier.  If you need lots of attenuation, like 30 dB or something, a more complex filtering device may be required.  If you whine also occurs on RX and this does not cure the problem, then you may need to look into the antenna, antenna coax, antenna ground, radio ground, etc. 
     I am not an expert on this, so do some research.  Lots of info available on the internet, ARRL publications, and possible even if you do a search on alternate whine (RFI) for your model of vehicle and/or the specific alternator.  Yes in the old days a single diode failure was not at all unusual.  Many decades ago a single automotive cap did solve a not too severe whine problem for me.  If the whine is only on TX the cap could probably be located anywhere in the power feed line, but probably best in the engine compartment where you can attach it to a good engine or frame ground point.  Probably not as effective in the passenger compartment since the ground point is questionable.  Attach the capacitor directly to ground, not even through a short ground wire.
               Rick  KL7CW
           
Logged
N8AUC
Member

Posts: 586




Ignore
« Reply #5 on: June 24, 2019, 01:17:34 PM »

I had that problem once with an Icom rig in a 2001 Ford Taurus. And you could hear it on receive too.
It got really annoying, and I tried several variations on rerouting the wiring trying to make the whine go away.
None of them worked. Even running the wiring direct to the car battery didn't work in this case. And the antenna
was a NMO mount drilled through the vehicle roof.

So I found the original version of this brute force filter on line, and since the parts cost was around $20 or so, I built one.
This filter works like a champ. If you've got alternator whine, this WILL make it go away.

http://www.sanantoniohams.org/tips/whine.htm

73 de N8AUC
Eric
« Last Edit: June 24, 2019, 01:24:16 PM by N8AUC » Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!