Discussion in 'General Technical Questions and Answers' started by ANCELB, Jul 26, 2017.
Would a modern Schottky be a suitable replacment for these Ge diodes?
I used to have a bird, and better than a thousand dollars worth of "slugs".
Then I realised that a thousand dollar linear or antenna would make my signal much louder.
Well, that's the thing about instrumentation, it can cost.
Esp. RF stuff.
I opened up a 100W H band slug and verified I could 'trim' it to a 50W slug using the internal OEM trimmer, so the slugs CAN go to double sensitivity safely as per OEM design. Verified the cal using a 100Mhz scope, 10:1 probe and a 3Ghz rated RF load. (100W). Did a FFT to calc for any harmonic errors on the CW but they were not significant.
The design for the mod is complete, here is the targeted feature set:
1) P-e-P with digital hang time cal.
2) Double sensitivity, 1x, and double range for a 4X use of a single slug. This is mapped via an EPROM table for accuracy on the meter movement and does not slow the meter movement time constant response like existing mods.
3) Internal full scale meter movement cal. ; allows for 3rd party meter use as well.
4) Power input via micro USB from a Powerbank or PC. USB Data lines provide TTL rs232 over USB to PC terminal program for RF power data logging at user set intervals to the PC and interactive control for custom data like average power over the last minute, or peak sampled RF power so far, or power up run time.
5) RGB LED provides color coded 'scale mode' indicator, flashes when P-e-P is active.
6) Meter movement over range is digitally clamped to protect the delicate movement.
7) Power down via power bank switch or pulling the USB reverts the Bird 43 to OEM behaviour.
8) Controls consist of just 2 tactile push buttons, one time calibration is done using 2 internal jumpers
9) Thermistor Temperature compensation to improve the 0.4%/°C error (I refrigerated it overnight and made a warm up Excel chart to find out). Had to solve a quadratic eq via Newton Raphson iteration to do the resistor network.
Now powering the mod. on the go will cost very very little and is very convenient with the ubiquitous mobile phone Powerbanks . If u slap on a cheap 5000mA bank it should last a very long time before needing charge.
I'll be starting a new thread about the build in the DIY & Homebrew forum