Building Better Radios ~ That should be our goal every time we contemplate a project. Often however, the road to quick satisfaction is paved with compromises not only in the design but in the final product.
Why does this happen? Well that is a question that would be answered depending on what you do on your day job. The politician would answer: Only I can fix this problem! The lawyers would yell it is the legal systems and so on.
But the real problem is that we have become the instant gratification and cut the corners crowd. Only do the minimum is the mantra. These actions make for a compromised situation and often result in a marginal radio.
In the last two days I have received three emails regarding providing help. Their inquiries involve projects I have done and that these hams are trying to replicate.
I laugh at times about how some of these inquiries progress. One email asked if I had any information, sketches etc. for larger size displays.
I had previously provided to this ham a sketch for a Color TFT 128x160 display. He got that working but wanted something with a larger array to make it easier to read. I sent him a you tube link to the Hybrid Wireless Display which uses the ILI9341 -- 3.2 inches and big printing and suggested he see if this fits the bill.
Well the email back was -- the display is FB but the sketch is only for one band and there is no provision to switch bands. I had to count to 10.
The request was for a larger display not a multi-band radio. Actually the sketch behind that display can do 5 bands selectable with a band switch. For the Hybrid I was only using one band. My next step was to send him the actual sketch --where my reading between the lines from him -- this is too complex!
A simple DPDT Toggle switch could be used with the sketch and provide just two bands with 1/2 the switch for the BPF/LPF selection. But I suspect that is still outside the realm.
The fundamental issue is that to get the full benefit of the larger display and multi-band operation definitely entails study, learning and tinkering. But those factors seem a bridge too far for many hams. Just give me the sketch, set up for my project and then go away Pete!
The second email is more curious as this ham based on some earlier postings is trying to build the J310 Direct Conversion Receiver. Nothing is coming through the pipeline. So we have the "usual suspects" such as wiring/soldering, right component at the wrong place and bad components.
One element is working and that is the audio amp, but the rest is as dead as a door nail. I was assured all the wiring was checked and that passed the smell test.
It seems he got the J310's from China and so that raises a flag. Then I asked about his LO source. Shudder ~ He is using his trusty Nano VNA. That raised another flag for me -- never trust the Nano VNA!
I made a couple of suggestions on how to tackle the problem. The 1st issue is the J310's -- are they working. From afar I could see a blank look on his face. So my suggestion was to build a crystal oscillator like this and test all of the J310's to see if they oscillate. If none of them oscillate then once again the Chinese suppliers have duped a poor American ham into buying defunct parts!
Oh yes the crystal -- literally any computer crystal in the range of 4 to 10MHz can be found at Mouser and Digi-Key and likely are less than a $1.
So once you have a go or no go then you can check that off the list. Assuming you had some that actually worked then it is time to focus on a real LO. He has the option of building a simple Analog LC VFO or perhaps a Si5351 with an LCD. Something more than a Nano VNA is needed for the J310 circuit development!
The Si5351 offers a wide range of frequencies with some accuracy as to the real frequency. But unless some measures are taken to assure you have good J310's you will continue with an inoperative circuit.
Often making stuff work is like a detective mystery where you have to look deep for clues. It also means that to be a detective requires knowledge and thinking beyond two J310's.
73's
Pete N6QW