Vintage radios vs new IC based

[OldskoolPirate]

Many moons ago I saw a post on here about new FM radios and how bad they are compared to old real component radios.

I’m wondering why new FM radios get so much hate. They seem to do as good of a job as old radios so what’s the issue ?

I might experiment using an fm radio as a short hop link system but will the modern circuitry be overloaded with RF, or could it be filtered out somehow ?

[Albert H]

Most transistor radios will suffer in close proximity to any kind of rig. Most modern receivers are pretty horrible (unless you pay £££).

[jvok]

I might experiment using an fm radio as a short hop link system but will the modern circuitry be overloaded with RF, or could it be filtered out somehow ?

There are a few world band radios from Tecsun which can receive the ex-soviet 66-74mhz and Japanese 76-88mhz bands so can be used for band I links. Useful if you want to keep your link out of the normal FM range, and being further out of band will help with overloading too.

You could also bodge in an external antenna jack so you can use a yagi pointed away from the main tx.

[OldskoolPirate]

Yeh I’m wondering if there’s some kind of choke i could build on the antenna input so it blocks everything but 1 frequency.

[jvok]

Something like this would work if you're running band I:

Not much use if your links in band ii though...

[Albert H]

The best frequencies for links are up in the TV bands (Bands IV and V) - there's lots of space up there, and TV Yagis never look out of place!

[OldskoolPirate]

Yes Albert, post a design and there might be a slight chance I’ll use it. I can’t design from scratch, I’m not as smart as you clearly. If I knew how I’d be doing it right now. If I start trying to figure out how to build a band 4 link it will take me years to design something decent and I just want to play music tbh. Band 1 is tried and tested, ready to go.

[jvok]

Is there really that much space left in the TV bands anymore? With the push to free up space for mobile data in the past few years e.g. 700mhz clearance, more and more muxes have been consolidated in bands IV/V. Looking at the ofcom data there's very few clear channels left in my area once you consider the several main transmitters plus relays that can be received here. I can only imagine its worse in major cities.

I guess yagis being more directional in TV bands helps a bit.

[Albert H]

The directionality of Yagis really helps, and if you look between the digital TV multiplexes, there are "guard bands" that are a couple of MHz wide in most cases. PLLs are easy enough up there - most of the prescaler chips work at up to at least 1 GHz. The only real hassle is that layout becomes really critical, and every component lead has significant inductance and capacitance to the groundplane. Transistors like the BFR91 / 96 work easily at up to 1 GHz, and 2N3866 is OK for 500 - 600 mW at 600 MHz.
Receivers are just a bit trickier, but my approach was to use Philips UV616 TV front-end feeding a mixer stage (35 MHz IF down to 10.7 MHz), then a standard IF strip. The '616 is tuned with another PLL......
The last one I built used 24-element TV Yagis (£9 each from B&Q) at each end, 2N3866 for the output of the TX, and the UV616 trick for the receiver, and linked fully noise-quietening FM stereo over a 11km path with ease one the aerials were aligned!