Fine tuning on the Ten-Tec 1253 is done with an additional
voltage control on the tuning varactor. This is a quite satisfactory
solution, in my opinion. You just have to remember to return the
fine tuning control to the center position before you move up
or down the band when scanning for additional stations.
The only clear problems that I experienced with the
Ten-tec 1253 were:
Lack of a shielded antenna connection - I added an
SO-259 connector to replace the binding post. A random length
wire can be attached through a banana plug.
Ugly tuning knob - a trip to Radio Shack fixed this.
I added the "enhanced sensitivity option."
I might want to re-think this. With it, the regeneration setting
is somewhat "twitchy."
Calibration required borrowing a signal generator from
a friend. I have to consult a chart for the band coverage. I simply
stuck a chart with the tuning ranges to the top of the receiver.
The second regenerative receiver kit I built was the
MFJ-8100. They take a slightly different tack in the design. They use a series of inductors with a simple
multi-position switch to tap into the inductor string for band
switching. They, as do Ten-tec, use simple ferrite miniature inductors,
except for one that is a toroid that you have to wind. All the
inductors in the Ten-tec 1254 design are miniature ferrite inductors.
MJF-8100 uses a nice variable capacitor with a vernier
reduction drive for tuning. This "feels" better than
the potentiometer used in the Ten-tec 1253. The tuning is a little
"fast" on the upper bands, but acceptable. I admit to
being a tradtionalist on the issue of real variable capacitors.
I am not sure God intended us to tune circuits with varactors.
The MFJ-8100 has five bands to cover most of the same range as
the Ten-tec 1253, but this is due to using a variable capacitor
instead of a varactor.
Again, lack of a shielded antenna connection. I added
an SO-259 connector on the back panel. I did retain the supplied
binding post for the antenna, however.
Lack of external power supply connection. A power jack
from Radio Shack and a SPDT toggle switch took care of this. I
can use an external 9 volt battery. There are eight screws to
remove to get the case apart to change the battery, so an external
battery is handy.
Exact calibration can effectively be done at one point.
I zero beat to WWV at 15 MHz. At worst, dial seems to be off by
+/- 200 kHz at the lowest or highest tunable frequencies. I made
a couple of dots with a marker for CW portions of the 40 and 20
meter bands for CW QRP monitoring.
Headphone only operation. A small external speaker/amplifier
from Radio Shack took care of this. I might add a more robust
internal AF amplifier, as there is plenty of room in the case.
A small speaker could be fitted as well. A project for the future...