[Boatanchors] OT : TVS DIODES

[WA5CAB at cs.com]

Various,

Actually, voltage regulation in nominal 12 volt vehicular systems doesn't 
(can't) qualify for "pretty good" as it varies from about 10.5 volts (engine 
off and battery near full discharge) to 13.8 to 14 volts (depending upon 
generator or alternator contractor).  Any decent HT or 12 V mobile rig should 
operate fine over that range.  For the HT not designed for the mobile 
environment, all that you should need is a spike suppressor to protect the fragile 
solid state radio if the engine is started while the radio is on.  Mobile 
rigs should have this built in, although it's a well known fact that the 
RT-524 did not.  Hence the requirement to add the MX-7778/GRC Transient 
Suppressor Assembly (main component is MX-7777(*)/GRC) to Vietnam era vehicles.  
Anyway, all that you should need to protect your rice burner HT is the 
equivalent to the MX-7777 (but probably at much lower power rating - the MX-7777 will 
run a GRC-106 and a VRC-46).  But no active components needed or even 
desired.  They just generate additional heat.

Robert D

In a message dated 09/10/2012 19:49:37 PM Central Daylight Time, 
jcoward5452 at aol.com writes: 
> The automobile regulation is pretty good even in the old VW's I drive. 
> I'd just add a series diode or two to drop the vehicle voltage to close to 
> 12V as is possible. The radio won't know the difference.
> Jay KE6PPF
> 
> 
> 
> -----Original Message-----
> From: W2HX <w2hx at w2hx.com>
> To: W2HX <w2hx at w2hx.com>; boatanchors <boatanchors at mailman.qth.net>; 
> kf4nsradio <kf4nsradio at verizon.net>
> Sent: Mon, Sep 10, 2012 5:21 pm
> Subject: Re: [Boatanchors] OT : TVS DIODES
> 
> 
> I ask because you cannot use a 7812 regulator on a 12V (or 13.8V source).  
> 
> ccording to the spec sheet, the 7812 requires 14.5V to maintain line 
> egulation. Basically the 7812 was not meant for use in an application like 
> 
> ours.  It was meant to regulate an input of 15 to 35V down to 12.
> 
> 3 Eugene W2HX
> 
> -----Original Message-----
> rom: boatanchors-bounces at mailman.qth.net 
> [mailto:boatanchors-bounces at mailman.qth.net] 
> n Behalf Of W2HX
> ent: Monday, September 10, 2012 6:24 PM
> o: boatanchors at mailman.qth.net; kf4nsradio at verizon.net
> ubject: Re: [Boatanchors] OT : TVS DIODES
> Is the application to eliminate a small battery on the radio for use with 
> an ac 
> ains source or a dc 12v of the vehicle?
> 73 Eugene W2HX
> -----Original Message-----
> rom: Dick KF4NS [kf4nsradio at verizon.net]
> eceived: Monday, 10 Sep 2012, 6:11pm
> o: boatanchors at mailman.qth.net [boatanchors at mailman.qth.net]
> ubject: [Boatanchors] OT : TVS DIODES
> I know this is a bit off topic but with all the knowledgeable guys here 
> when it 
> omes to some of  the new stuff, I hope someone can help.
> I have put together a battery eliminator for use of my HT in the car, 
> built into 
> gutted battery pack. I have all the components selected including ferrite 
> eads for the + - leads from the cigar lighter which is fused at 2A, fed to 
> a 
> 812 regulator having in and out capacitors as recommended in the 
> applications 
> age from the spec sheet.
> It has come to my attention that I could protect the input from EMI RFI 
> and 
> urge by adding a TVS diode in the power leads. After studying the wealth 
> of 
> nformation available on the INET, I am so confused about how to choose the 
> 
> ppropriate diode. The filters that Mouser lists for selection of a diode 
> have 
> eft me totally in doubt. I am referring  to the INFINEON brand of  diodes.
> Anyone with any experience and advice to share would be greatly 
> appreciated.
> 73, Dick KF4NS
> t Petersburg, FL 33714 USA
> eep The Glow!
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480