Filter.

Because of all the harmonic some filtering is required.

I decided to use a combination of high-pass and low-pass filter.   The most important about the filters is to get the harmonics down with at least -60dB or better than the local oscillator frequency. The reason for this LP/HP combination is that the filters is simpler to trim and the band-pass is simpler to adjust, the drawback is some higher losses.But since I will use a buffer amp after the filters a loss of a few dB is not the big concern. The filters where designed with AADE filter software.

 

Schematics and plot for high pass filter.

EHP 40mhz

Schematics and plot for low pass filter.

ELP 43mhz a

The EHP 40mhz must be renamed from .key to .sch to be able to open it in AADE filter software.

Trace.

Trace of filter smoothed with 100 samples.

Trace of filter and oscillator smoothed with 100 samples.

 

As you can see there is a bit of loss in the filters, but I’ll make a tuned input buffer amp to get rid of the harmonics on 14 MHz, 56 MHz and 84 MHz.

Oscillator multiplier.

Here is the schematics of the oscillator multiplier. It multiplies from 14MHz to 42 MHz.

The design of the multiplier gives a lot of harmonics all the way up to the 21 order at 294 MHz. This might be a good oscillator for transverters all the way up to the 23cm band with a 2GHz transistor. The output transformer will have to be an air-core transformer.

Quick about the circuit.

R1: 47Ω

R2: 10kΩ

R3: 4k7Ω

R4: 300Ω

C1: 0,1μF

C2: 45,5 pF @ 14MHz or 30,32 pF @ 21MHz. I used a 50 pF trimmer.

C3: Ca 40pF @ 14MHz or 50pF @ 21MHz.

T1:  250Ω 14 MHz; 2,83μH, 19T 10mm core 12 mm long. 0,202mm enameled cu wire. Secondary is 10-20% of primary.

T1: 250Ω 21 MHz; 1,89μH, 14T 10mm core 9 mm long. 0,202mm enameled cu wire. Secondary is 10-20% of primary.

To calculate the I used two web pages. The Daycounter for calculating the required inductance and www.circuits.dk to calculate number of turns on the inductor.

66pacific.com does also have a good calculator to reverse engineer the inductors in the schematics.

As showed in the picture there are harmonics up to 21 order, the harmonics over 14 order are more or less neglectable.