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Fellow enthusiasts,
My FT-980 has a curious ailment and I'm hoping someone here can offer some guidance. In order to communicate on, say, 3.595000MHz, I need to tune my rig such that the frequency display reads 3.595250MHz. Having listened to my own transmissions on a websdr station not far away, I've verified that the 250Hz offset produces a good signal on the desired 3.595000MHz. Shifting to 40m, the offset appears to be 500Hz such that, to achieve comms on, say, 7.160000MHz,I need to set my display to 7.160500MHz. On 20m, although I haven't verified quite as methodically as for 80m and 40m, it appears that I need to set my display frequency a whole 1kHz above my desired frequency. That there appears to be a mathematical relationship in all of this, I suspect that some simple might need to be adjusted. But what, I don't know. For the record, there is no clarifier/RIT in play. I know I can use the rig without trouble by remembering to dial higher, but I'd like to get the rig back into line as it is otherwise in mint condition. Any clues would be much appreciated.? Thanks, Mark VK2MOH |
开云体育check reference oscillator frequency. forgot the frequency, replaced mine 25 yrs ago or so bob d wb3hyb On Sep 12, 2020, at 4:22 AM, VK2MOH <vk2moh@...> wrote:
?Fellow enthusiasts, My FT-980 has a curious ailment and I'm hoping someone here can offer some guidance. In order to communicate on, say, 3.595000MHz, I need to tune my rig such that the frequency display reads 3.595250MHz. Having listened to my own transmissions on a websdr station not far away, I've verified that the 250Hz offset produces a good signal on the desired 3.595000MHz. Shifting to 40m, the offset appears to be 500Hz such that, to achieve comms on, say, 7.160000MHz,I need to set my display to 7.160500MHz. On 20m, although I haven't verified quite as methodically as for 80m and 40m, it appears that I need to set my display frequency a whole 1kHz above my desired frequency. That there appears to be a mathematical relationship in all of this, I suspect that some simple might need to be adjusted. But what, I don't know. For the record, there is no clarifier/RIT in play. I know I can use the rig without trouble by remembering to dial higher, but I'd like to get the rig back into line as it is otherwise in mint condition. Any clues would be much appreciated.? Thanks, Mark VK2MOH |
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Hi Mark,
The heated 30MHz master crystal will drift over time as it (and other components like the pulling caps) age. After almost 40 years this drift will probably be signficant (it certainly was in my FT-980). I included an article in the "Repair" folder in the files section on how to "re-calibrate" it, along with what to do if the drift exceeds the stock trimmer-cap adjustment capability. -Mat N8TW |
开云体育Thank you Robert & Mat.? I’ll try the trimmer cap first to see what effect it has on the displayed frequency.? In the meantime, a more impacting challenge has arisen... weak modulation on AM.? With Mic Gain at max, people comment on poor modulation. I can’t get any action on the ALC meter in AM and need to almost shout to get it moving on SSB. ? Given your respective experiences, any clues will be appreciated.? If it’s significant, the unit was built in 1985.? All the best, Mark VK2MOH On 2 Jan 2021, at 02:24, Mat Breton <i.m.n8tw@...> wrote:
?Hi Mark, The heated 30MHz master crystal will drift over time as it (and other components like the pulling caps) age. After almost 40 years this drift will probably be signficant (it certainly was in my FT-980). I included an article in the "Repair" folder in the files section on how to "re-calibrate" it, along with what to do if the drift exceeds the stock trimmer-cap adjustment capability. -Mat N8TW |
Mat Breton N8TW