Wouldn't hurt ... but if you want the AFC to work properly, you will need to change the direction of the discriminator diodes. Neil -
----- Original Message ----- From: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]> Date: Tuesday, November 28, 2006 7:31 am Subject: Re: [Repeater-Builder] Re: spur from UHF MASTR II mobile - link radio > Should the same high-side injection be requested when ordering 440- > 450 MHz crystals for a MICOR channel element? So far, everything > has tuned up very well just having ICM make new crystals according > to the standard MICOR receiver formula, and I always send in the > channel elements to be completely temperature compensated, etc. > while I'm at it. But I've wondered if future orders should also > request that they be ordered with high-side injection? > > LJ > > > ----Original Message----- > >From: k6jsi <[EMAIL PROTECTED]> > >Sent: Nov 27, 2006 9:00 PM > >To: [email protected] > >Subject: [Repeater-Builder] Re: spur from UHF MASTR II mobile - > link radio > > > >--- In [email protected], "Don Kupferschmidt" > ><[EMAIL PROTECTED]> wrote: > >> > >> Nate, > >> > >> I'm wondering if you can point me to a link that would further > >explain lo / > >> hi injection. Hate to admit, but I'm not all that familiar > about > >the > >> subject, especially in repeater operation. > >> > >> TIA, > >> > >> Don, KD9PT > >> > >> > > (Snip) > > > >Hi Don, > > > >The normal MASTR II receiver uses a low-side Local Oscillator > >injection for their mixer. The IF is 11.2 MHz, so you deduct > 11.2 > >MHz from the operating frequency. The normal operating frequency > >for the 88 series MASTR II radios is 450 to 470, so the LO (Local > >Oscillator) is engineered to run between 438.8 and 458.8 MHz (450 ? > >11.2 = 438.8; and 470 ?11.2 = 458.8). > > > >When we in the amateur radio service order a low-side injection > >crystal, we are essentially asking the LO to operate between > 428.8 > >and 438.8 MHz, worst case being 10 MHz below the engineered > >operating frequency range (440 ?11.2 = 428.8, and 450 ?11.2 = > >438.8) This is stretching the original design of the local > >oscillator 10 MHz beyond the design parameters. > > > >If we order high-side injection crystals, we add 11.2 MHz to our > >operating frequency, rather than subtract it. So the LO will > runs > >between 451.2 and 461.2 MHz (440 + 11.2 = 451.2, and 450 +11.2 = > >462.2). > > > >If you are operating in an area of the country where you run low- > in, > >high-out split repeaters, your receivers will operate between 440 > >and 445 MHz, and the highest possible LO frequency will be 456.2 > MHz > >(445 + 11.2 = 456.2), or right in the sweet spot for the LO range > >(438.8 and 458.8). > > > >If you are operating in an area of the country where you run high- > >in, low-out split repeaters, and your receiver will operate > between > >445 and 450 MHz, and the highest possible LO frequency will be > 450 + > >11.2 = 462.2, or only 3.4 MHz higher than the designed frequency > of > >the LO. > > > >The cross-over frequency seems to be 448.300 MHz, which is 1.7 > MHz > >higher at a high-side injection than designed, and a low-side > >injection is 1.7 MHz lower than designed Local Oscillator. > > > >So, maybe a good rule of thumb would be to order high-side > injection > >on operating frequencies below 448.300, and low-side injection on > >receive frequencies above 448.300. That way, the worst case > >scenario is your being either 1.7 MHz higher or lower than the > >original engineered design on the local oscillator. > > > >You can do the same math for high-band radios. Same IF. > > > >Hope that helps. > > > > > > > > > > > Yahoo! Groups Links > > > >
