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Title: RF MOD MTR..where was this used..?? Post by: wb1ead on May 24, 2022, 01:58:22 PM Hello all..hope everyone is doing OK..bought a huge slug of vacuum tubes Sun at a local flea mrkt..inside one of the boxes was this meter..made by Texas Instruments..measures Carrier RF from 0 to 200 watts on top scale..0 to 100% mod on bottom scale..is approx 2" across with a brass screw-on outer ring..it is functional and not seized up..model number is A85x34 and inside under the glass it says model 321..f.s=200ua..I simply cannot supply a picture as no capability here..I wud take a guess as Mil from the 40s to 70s..???? any thoughts ? TNX ! 73 de DAVE WB1EAD
Title: Re: RF MOD MTR..where was this used..?? Post by: WD5JKO on June 19, 2022, 04:23:43 PM Dave,
My guess is is just 200ua full scale, and likely 50mv across the terminals when at full scale. The meter ranges are custom to the application, so long as 0-200ua criteria is met. A 9 volt battery and a series 100K resistor should pass 90ua, or just a little less than mid scale reading. As far as the huge slug of tubes, any chance you have any type 6HR6? :D This is a pin-out equivalent to a 6BA6 but with higher gain. Jim Wd5JKO Title: Re: RF MOD MTR..where was this used..?? Post by: wb1ead on June 20, 2022, 10:08:09 AM Tnx Jim for chiming in..I did try a button battery with a similar resistor..came up half scale so I'm assuming it's working OK.. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
sorry no 6HR6 here..closest is 6HS6..same basing..wow looked at the retailer of tubes online..big time price there !! Where the mtr came from remains a mystery..73 de DAVE WB1EAD |