Very nice vintage dip oscillator - these were originally called Grid Dip Oscillator, being valve based originally but this one is semiconductor based.
It is old but still very useful for the following:
Finding resonance of a tuned circuit, antenna's and coaxial feeders
Absorption Wavemeter to check the oscillator & output frequency from transmitters
Short Wave (HF) Signal generator, either carrier only or with a switchable 2Khz tone (AM mode)
Monitor of AM transmitter signals using the crystal earphone socket
Fixed Frequency crystal oscillator - instead of a coil, insert a crystal of any frequency between 1 - 15Mhz
Audio only output - the 2Khz tone is available at the phone jack, for checking audio circuits
Inductance tester, using a known capacitance it is then possible to calculate the inductance when resonance is found
Capacitance tester, same as with inductance but with a known value of L and then calculating C
LEADER Dip Oscillator (commonly still referred to as a Grid Dip Oscillator)
Leader Instruments
Made in Japan
Circa early 1970's
Model: LDM-815
Suitable for use from 1.5Mhz to 250Mhz
Complete with all 6 coils (one for each frequency range)
THE FT-243 adaptor plug is missing. This is only required if the user intends to test crystals of various sizes. Adaptors to suit are very easy to obtain if this is important for the user.
Complete with the original user manual, which includes a comprehensive "how to use" set of instructions, block diagram, circuit diagram with all values and a parts list
Complete with the original box and packaging
COSMETIC CONDITION:
Excellent condition, the box is a bit "50 years old" but still holding it together. The instrument is in excellent condition in all respects
TESTING:
It has been a long time since this has been turned on.
Inserting the battery is a pain quite frankly so I have left the battery sitting to the side for my tests.
To access the internals, two screws need taking out - off comes the side panel and then you need to remove the battery bracket and then reassemble everything.
9V battery is required - battery clips are not corroded or damaged
Battery test is fine
Made a very simple LC tuned circuit and then went "dipping" using the highest frequency range. I found resonance at 225Mhz very easily - the dip is pronounced and not easy to miss!
I then undertook some more basic resonance tests to check the oscillator was working, it is - no issues at all, nice dipper!
NOTE: The "tightness" of coupling to the LC circuit is critical to obtaining an accurate reading - keep this in mind when using these.
Checked the 2Khz audio output, that is also fine.
I don't have any HF signal source at the moment, let alone AM or CW so I couldn't check the functions such as checking transmitter output etc but based on the resonance test results, I have no doubts these features work properly as well.
Great piece of vintage gear that is still useful, especially for those playing in the HF bands, up to VHF.
