Re: [Repeater-Builder] Hamtronics exciter

[Kevin Custer]

Hi Steve, I have had good results FM'ing the TA-51 and TA-451.  See here: http://www.repeater-builder.com/rbtip/ta-51pl_mod.html While this mod was only intended for FM'ing the crystal to get adequate PL deviation with low distortion, I have recently redone my remote receiver projects for one of my 2 meter machines (4 sites).  I used the modification as above for voice frequencies as well as PL, the difference from the stock modulator was amazing.  While the linearity of the modulator 'as designed' is of no concern when only one frequency is applied (like a PL tone) I was surprised to measure quite acceptable response across the entire range from about 10 cycles to about 5500 cycles.  Even though the PM modulator in the UHF exciter shows better response because it's multiplied several more times then on low-band or high-band, FM'ing it made it sound so much better.   Obviously, a clipper and low pass filter should be implemented when using any modulator capable of deviating beyond the acceptable bandwidth of the particular service/frequency spectrum. Kevin Custer Steve Grantham wrote: Well...  Does anyone think it would be feasible or practical to modify the TA-51 to implement an LC phase modulator?  Just how easy or how difficult might that be?   Steve ----- Original Message ----- From: Kevin Custer To: Repeater-Builder@yahoogroups.com Sent: Tuesday, April 13, 2004 9:46 PM Subject: Re: [Repeater-Builder] Hamtronics exciter [EMAIL PROTECTED] wrote: Hi Kevin,   Virgil mentioned that he had looked at the manual and noted that the TA-51 uses RC phase modulation. A-ha! The light went on. You can only get 90 degrees of phase shift max with an RC circuit. Had they used an LC phase modulator, they would have gotten 180 degrees max. That's why the deviation is low with that unit. They don't have much deviation to start with, and as you say, if it isn't multiplied a lot, it'll be low at the final freq. Tell Virgil thanks for the investigation.  Also as a side note from practical experience with this type of exciter, and as you have mentioned before as well, the tuning of the first stages after the oscillator are critical for good modulation, otherwise it will be very distorted. Kevin Yahoo! Groups Links To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/   To unsubscribe from this group, send an email to: [EMAIL PROTECTED]   Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.