[Heath] Fw: Heathkit SB-610

[Morris]

I may be wrong but I've always expected the capacitance of coax to be
expressed from shield to center conductor, not serially.  In this case you
would not have a simple series connection of two capacitors and the
equipment in question.

Morris 



> -----Original Message-----
> From: heath-bounces at puck.nether.net 
> [mailto:heath-bounces at puck.nether.net] On Behalf Of Dick KF4NS
> Sent: Wednesday, March 07, 2012 2:43 PM
> To: ma.locksmith at juno.com
> Cc: Heath puck list; heathkit at mailman.qth.net
> Subject: [Heath] Fw: Heathkit SB-610
> 
> 
> Ok guys, most responses have been related to the coax. Since 
> there is no loss in the 610 and the vert amp 
> is doing its job the loss is obviously in the originating 
> equipment. Also, Heath does not say you should 
> use RG-62, it only mentions the best coax for the xmit 
> input/output. There they say to use 50 or 75 ohm 
> coax.
> 
> I was doing some thinking (bad for someone my age) and 
> remembering electronics school, as I recall 
> capacitors in series are equal to a value lower than the 
> lowest capacitance. (smaller than the smallest 
> as I remember) so my 5uuf cap in series with the 93ohm coax 
> should result in total capacitance less than 
> the 5uuf cap in series.
> 
> Hmmmm! Is my age showing or am I thinking correctly. Some 
> have said they use all different types of coax 
> with no trouble. What if I used just a piece of insulated 
> wire from the 2nd IF to the jack on the xcvr 
> back and use coax from there to the 610 ?
> 
> 73, Dick KF4NS
> St Petersburg, FL 33714 USA
> Keep The Glow!
> 
> 
> ----- Original Message ----- 
> From: <ma.locksmith at juno.com>
> To: <kf4nsradio at verizon.net>
> Sent: Tuesday, March 06, 2012 6:52 PM
> Subject: Re: [Heath] Heathkit SB-610
> 
> 
> | Yes, the coax IS faulty....  but, not because it's broken
> |
> | You have selected wiring with very high capacitance.  This makes a 
> | capacitive divider for the signal.  If you only have 5 pF 
> capacitance 
> | in the cable, you have a 2:1 reduction in signal strength.
> |
> | RG174 and RG58 have high values.  I think the 58 is 32 pF 
> per foot.  
> | Not sure about the 174 unless I look it up.
> |
> | I expect the "right" cable between the set and the 610 will 
> be RG 62. 
> | And, more than likely, unshielded wire inside.
> |
> | Ed
> | K1ZOK
> |
> | On Tue, 06 Mar 2012 15:58:50 -0500 "Dick KF4NS" 
> | <kf4nsradio at verizon.net>
> | writes:
> | > Looking for your input and recollection of what you did. 
> I have now 
> | > completed a full restoration of my SB-610 and have concluded that 
> | > the one remaining fault, low vertical gain, may  be due to how I 
> | > have connected it to my HW100.
> | >
> | > It did work pretty good at one time so now there is a bit of head 
> | > scratching. I  have no losses in the 610 and the vertical 
> amp, when 
> | > driven with a sig gen at 3395khz modulated at 50%, I see 
> .4v (spec.
> | > recommends .5v input) at the grid and get 23v at the plate. That
> | > sounds like the 610 is doing the job.
> | > The vertical gain pot is fine. So now I suspect it has to be the
> | > connection to the rig.
> | >
> | > I used RG-174 in the HW100 from the second IF plate and 
> have a 5uuf 
> | > cap in between. Outside the rig I have a short run of 
> RG-58 to the 
> | > 610. I can only see .1v from the rig. The coax is not 
> faulty nor is 
> | > the capacitor.
> | >
> | > What did you use in your Heathkit rig for coax and 
> coupling cap. and 
> | > what did you feed the 610 with? Did you connect to the first or 
> | > second IF and at the control grid or the plate? I did do a mod to 
> | > the 100 which lowers the IF gain to improve gain 
> distribution. This 
> | > came from my friend Mark's (WB8JKR now SK)
> | > presentation for optimizing the HW/SB transceivers. When the scope
> | > was working fairly good this mod was
> | > already there. I did realign the rig though at some point since
> | > then. The 100 is working great.
> | >
> | > Thanks and 73, Dick KF4NS
> | > St Petersburg, FL 33714 USA
> | > Keep The Glow!
> | >
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