[HBR] Tuning Rate and Bandspread Specification

[n2ey at aol.com]

There was a question about "bandspread" - but I think it was really about tuning rate.
 
The way I've always specified tuning rate is "kc per knob turn" - how many kilocycles one complete 360 degree rotation will take you. Since few designs are truly linear, this is often a range, such as "16 to 20 kc per knob turn". 
 
The Southgate Type 7 uses the capacitor from a BC-221 freqmeter. About 5 kc. per knob turn (4 to 6, depending on which end of the dial). Just about right for CW operation IMHO. 
 
Older rigs tended to have "fast tuning" - often as fast as 100 kc per turn! I think this was due to
both economy factors and the type of operation that was common in the old days, when transmitter
QSY was difficult-to-impossible, and one tuned the whole band after a CQ.
 
"Bandspread", as I learned it, is a measure of how much a given number of kc are spread out on the dial.
If a linear dial 5" long covers a 500 kc. band, the bandspread is therefore 100 kc per inch.
 
The Southgate Type 7 uses a circular drum dial 6" in diameter, and a band of about 250 kc. is spread out over a half-revolution of the dial. Works out to about 25 kc. per inch. 
 
73 de Jim, N2EY