Re: [Drakelist] Drake TR7 and R7
I'd say the rig was used for swl purposes, and the owner was trying to get maximum sensitivity out of it, although questionable how much more, if any. I seem to remember this mod on one of the swl lists/sites. David Wd9cmd - Original Message - From: Jim Shorney [EMAIL PROTECTED] To: drakelist@zerobeat.net Sent: Wednesday, December 03, 2008 9:56 PM Subject: Re: [Drakelist] Drake TR7 and R7 Hi John, On Wed, 3 Dec 2008 21:06:24 -, John Stringer wrote: 1. The RIT on the R7 should be about plus or minus 3khz It has been modified to plus or minus 200hz. Yes 200hz. Why? Probably the same reason I reduced the range on the RIT control in my HR2510. WHen using the RIT as a fine tune control, you're not usually going more than a couple of hundred Hertz, at the most. There's really not much need for 6 KHz of range, and reducing the range makes it easier to fine tune with that tiny knob. 2. An SO239 has been installed on the back panel A. Connect the antenna to the SO239 so bypassing the Antenna Switch. B.Install a jumper between the SO239 and the spare RCA socket and put the antenna into its proper RCA connector so routing the antenna via the Antenna Switch--in other words the normal way. That's an interesting one. My fisrt thought is to allow the user to bypass the antenna selector, as the splitter has some loss through it. There is theoretical 3 dB dignal drop through any two-way splitter (half the signal goes to each port), plus circuit losses, which typically adds up to 3.5 to 4 dB in the real world. However, I was looking at the schematic just a couple of nights ago, and it appears that the splitter circuit is bypassed when the antenna selector is set to Main/Alt ... which would make sense. This would leave and small (probably insignifigant) loss in the cables and switch itself. In light of that, the only thing that really makes sense me is pehaps the owner wanted to use the antenna selector to feed two other radios other than the R7 from one of two antennas, at the same time the R7 was being used on a third antenna. Or maybe that it was an easy place to put a real antenna connector, and the owner elected to bypass what was essentially an unused feature when the radio was used in that configuration, or the isolation between ports wasn't sufficient for some reason. Maybe someone else has a more obscure reason? 73 -Jim NU0C ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR7 audio oscillation
Harold, I am not sure if that ferrite core will work in this application, nor can I say I have heard or seen such for an internal problem. With those older TR7's, the ferrite core solution sounds like a bandaid where surgery is required. If I had to venture a guess I would say it sounds more like a board seating issue to the mother board or a loose solder connection on one of the boards that creates the oscillation after the internal temperature rises and cause the boards to shift a little. Ron / WB4HFN - Original Message - From: hpolkscw [EMAIL PROTECTED] To: drakelist@zerobeat.net Sent: Thursday, December 4, 2008 10:02:58 AM GMT -05:00 US/Canada Eastern Subject: [Drakelist] TR7 audio oscillation I have a TR-7, serial, 45XX, that breaks into oscillation on both receive and transmit after some time warming up. However, it sometimes howls from startup. I remember reading some messages some time ago about a fix, which I think was a ferrite bead on a component leg. However, I cannot find this message after much searching, both on my computer and the archives. Can anyone point me in the direction of the message or provide the particulars of the modification. Thanks Harold N3HP ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR7 audio oscillation
Harold - I don't recall a ferrite bead fix. Often this sort of problem is the result of leaky T/R transistors (fuses!) Q306 Q307 on the Transmit/Exciter board allowing BOTH transmit and receive functions to sorta work at the same time. Check the 10R and 10T busses on the parent board. Each should read near +10V when it should be ON, and less than 0.1V when it should be off OFF. 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 4-B, C-Line TR-4/C Service Supplement CDs www.k4oah.com hpolkscw wrote: I have a TR-7, serial, 45XX, that breaks into oscillation on both receive and transmit after some time warming up. However, it sometimes howls from startup. I remember reading some messages some time ago about a fix, which I think was a ferrite bead on a component leg. However, I cannot find this message after much searching, both on my computer and the archives. Can anyone point me in the direction of the message or provide the particulars of the modification. Thanks Harold N3HP ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR7A AM problem
On Mon, 1 Dec 2008 16:30:23 -0600, [EMAIL PROTECTED] wrote: I've got a TR7A that works good on SSB, but AM transmit is problematic. I have to keep changing the carrier level control to get it to work. I've cleaned the control and aligned the radio, even changed a couple of caps to get the 40mhz oscillator and BFO both dead on. It also acts different from dummy load to antenna (only on AM). Anyone else had or have a similar problem? I haven't seen anyone tackle this yet, so I'll take a stab at it. Under what conditions do you have to change the carrier level? Band change, frequency change, antenna change, SWR change, etc? The amount of carrier that you need is dependent on the PEP output level that is available in SSB mode. This level is determined by the ALC circuit. ALC is derived from the forward and reflected power sensors for the built-in wattmeter. Anything that changes the output levels of the wattmeter sensors can change the ALC level and the maximum PEP power available. It will tend to vary by band and antenna SWR. So, some change when operating parameters change is normal. If it is changing from day to day on the same antenna, band, and frequency, you may have a problem somewhere. Hope this helps. 73 -Jim NU0C ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
