Project adaptation to R&S EK071

[ultravy]

Hello. i want to thank you for your project.

I want adapt this to a EK071 receiver - basically a EK070 but with different front panel with bcd switches.

I tried couple of times with two different arduino boards, but i had no luck! i tried only to connect first to 100 hz . No matter how many changes i've done to the code - using chat gpt (i'm not good at programing), the receiver freaks out and it start running BITE test...
Thanks in advance .

[d3rail0]

Hello @ultravy, glad you're finding the project interesting.
I looked at the technical docs.

Front panel has a knob that you should manually set to "FERN" (REMOTE).
This will lock up your control from the front panel and all tuning, channel, and frequency data will need to come from the external BCD interface.

Problem is that the INTERFACE EK071 J5 on the back panel doesn't allow direct 22-bit BCD control. It's not even a frequency input. Instead, it's an 8-bit BCD channel-number input:

• "Kanal" - Channel (1-255) (8bits; active HIGH) -> used to select preset memory channel to load.
• +5.3V (1 pin) -> supply reference for pull-ups (22kΩ)
• Ground (1 pin) -> logic return.

Channels are just stored receiver configurations using front panel controls. The remote control allows you to just switch between these presets by selecting them using the 8-bit BCD. It doesn't "tune" in a continuous way.

Due to the design of EK 071, RF-550 VFO tuner project cannot be ported directly, because the two radios expose completely different control interfaces.

The only way it could is if you were to make a hardware mod internally and tap the synthesizer's 22-bit BCD bus and override it. That is non-trivial and carries risk of damaging the synthesizer or the CPU interface.

[ultravy]

Hello. Ive done some measurements on the voltage on the bcd switches : The 2 1 8 4 are the bits connections to bcd switch itself. After i took out the switch, on the pcb connections the bits are literally marked, so this confirm my measurements are good . The 0,1,2,3,4,5,6,7,8,9 is the number selected on the switch. The "+" is the line of 5.2 v, from where the bcd is taking power and rerouting this from the number selected to the respective bits . This matches with the binary code on listed on the harris service manual https://freeimage.host/i/KbTFxJj . but i didn't went further in to harris manual. The kanal - channel - is actually working . It has 50 memories that can be stored, including frequency , mode (AM for ex) agc position, filter and attenuator even! When you set everything just push store - is a small button that can be accessed with a tip of a pen or small screwdriver - and everything is stored.

nr bits
all + 2 1 8 4

0 5 5 5 5 5

1 5 5 0 5 5

2 5 0 5 5 5

3 5 0 0 5 5

4 5 5 5 5 0

5 5 5 0 5 0

6 5 0 5 5 0

7 5 0 0 5 0

8 5 5 5 0 5

9 5 5 0 0 5

[d3rail0]

That's great. Your measurements line up perfectly with the RF-550's BCD logic. Bits are active-low and already have the internal pull-ups. If you are planning to "inject" an Arduino here, you must present an open-collector drive. You'd need 4 NPNs per digit (or a transistor array).

You could emulate this with Arduino as well, but with a little mistake (or Arduino quirk) you could source +5V into the circuit, or sink more than 20 mA into Arduino (its absolute max).

Software-only open-colector emulation (ok for prototype, but I suggest NPNs):

void setup() {
	for (int i = 0; i < 4; i++) {
		// start released (float/high)
		pinMode(bitPins[i], INPUT);
	}
}

void setDigit(uint8_t value) {
	// ... here use logic to figure 8421 bits
	bool bits[4] = {b8, b4, b2, b1};
	for (int i = 0; i < 4; i++) {
		if (bits[i]) {
			// logic 1 - pull the pad LOW
			// make sure it outputs 0 V
			digitalWrite(bitPins[i], LOW);
			// enable sinking
			pinMode(bitPins[i], OUTPUT);     
		} else {
			// logic 0 -> release line (float/high)
			// tri-state, lets radio's pull-up raise it
			pinMode(bitPins[i], INPUT);      
		}
	}
}

tl;dr: If bit = 1 => pull LOW via NPN so that you only sink those lines. Avoid emulation.

[ultravy]

Thanks for the answer. Sorry for the late reply. So the "chatgpt" was right . When i first use it it suggest using a ULN2803A ic. Bare in mind that im not that advanced in electronics, but i can sort this out. I will have to order 4 ics for now, and start working on the project. I will post here the results.

[ultravy]

Hello. I
m sorry that it took me long time , but i finally got the time for it. I worked on different projects as well in mean time. I restored couple of receivers . I've spend couple of day on it, but no chance.... tried different code, used the ULN2803A. I tried resistors in between uln chip and receiver . I run out of ideas ! The receiver is stubborn and it would still go in to self test mode. i haven't tried with all connections. I only used last two digits , and then i tried mhz range, but no go! It seems the only way is to use a vfo with si5351. I will need to design and build a filter for 81.4 - 111,4 mhz . The LO output is 0 dB .