CSM(r) Gary Huber
glhuber at msn.com
Wed Jul 6 05:48:12 PDT 2011
>Thank you for your input and expertise Gary but I still don't see how the PBT setting would be correct for one filter (500 hz filter - PBT control at either 11 or 1 o'clock depending on >the band) and not correct for the other filter (250 hz) unless the center frequency of the two filters is different.
And that can be part of the problem, you do have to know which CW filter you have in the 250 HZ Position? There are two that will work, the 219 and the 221.
"What's the difference between the 219 and 221 filters?
If you usually run your CW offset at 500 Hz or less, and want to install both the 282 filter and a 9 MHz I-F 250 Hz filter, use the 221 instead of the 219. If you normally run CW offset at higher than 500 Hz, use model 219. Only the Omni-VI and Omni-VI Plus offer variable CW offset; offset on other Ten-Tec transceivers is fixed at 600 to 750 Hz depending upon model. The 221 filter is only for use with low CW offset on the Omni-VI and Omni-VI Plus." see http://tentecwiki.org/webarchive/filterhelp/
73 es DX,
Gary - AB9M
From: Keith Hamilton
Sent: Tuesday, July 05, 2011 11:40 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Correction
Thank you for your input and expertise Gary but I still don't see how the PBT setting would be correct for one filter (500 hz filter - PBT control at either 11 or 1 o'clock depending on the band) and not correct for the other filter (250 hz) unless the center frequency of the two filters is different.
On Jul 6, 2011, at 12:16 AM, CSM(r) Gary Huber wrote:
> Or you could just re-read closely the Ten-Tec owner's manual and note the
> recommendation to move the PBT to either 11 or 1 o'clock depending upon the
> band you are using and the sideband the CW is offset from the carrier
> 73 es DX,
> Gary - AB9M (a 30 year veteran with TT radios)
> -----Original Message-----
> From: Ken Brown
> Sent: Tuesday, July 05, 2011 10:50 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Correction
> Hi Keith,
> There are three things which determine the audio frequency of the CW
> note you hear when listening to a CW signal with an Omni VI. Those three
> things are:
> 1) The RF frequency of the signal you are listening to,
> 2) The LO frequency that the Omni VI is generating,
> 3) The BFO frequency that the Omni VI is generating.
> The amplitude of the audio you hear is affected by many things. For this
> discussion the most relevant thing is where the bandpass of the 9 MHz
> filter is relative to where the LO has converted the incoming RF, AND
> the setting of the PBT which moves the signals passing through the 9 MHz
> IF around relative to the center of the 6.3 MHz filter in use.
> When you have the PBT set for maximum "band noise" amplitude passing
> through both the 9 MHz IF filter and the 6.3 MHz IF filter, the the two
> IF bandpasses are as coincident as you can get them. The "center
> frequency" of this noise should be equal to the sidetone frequency that
> the Omni VI generates when you key it, and if you zero beat an incoming
> CW signal to your sidetone when you transmit your signal should be
> pretty near (in your case, being a piano tuner, damned near exactly)
> zero beat on the signal you have tuned in.
> Assuming that the Omni VI LO system is working right there are two
> things you need to do to get the frequencies to work out right.
> First you need to use the menu function that sets the sidetone
> frequency. This controls the offset of the LO system when you switch
> from receive to transmit, as well as controlling the frequency of the
> sidetone generated.
> Second you need to have you BFO crystal oscillators operating at the
> correct frequencies. The are adjustable with trimmer capacitors.
> You can always get the 6.3 MHz and 9 MHz IFs coincident by adjusting the
> PBT control, but when using a narrow 9 MHz filter you are stuck with the
> tone that passes through it. The best bet is to set your sidetone to
> match that.
> You could misalign your BFO to get the tone you prefer, and then set the
> sidetone to match it, but if you do your frequency readout would be
> incorrect by the amount you have misaligned the BFO. The BFO changes
> frequency also between transmit and receive, so you would probably have
> to misalign both frequencies equally to keep the zero beat with the
> sidetone exact, and this would result in incorrect frequency display for
> transmit as well as receive. If you stay far enough from the band edges
> it would not be a problem.
> I hope this helps,
> Ken N6KB
> Keith Hamilton wrote:
>> I made a typo in my question. I meant to say I must tune the radio from
>> 7.040.00 to 7.040.20 to center the 250 hz filter.
>> Keith W8GX
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