13 September 2018

Rethinking my mobile setup

Alright, the shortened UHF-only Nagoya UT-106 is back in service.

I added a piece of RG-58 with PL-259 so that I could measure SWR. But just the fact of terminating the coax with a PL-259 made me think of a way to fit the QYT KT-8900 mobile in the new car in place of a handheld.

While the large glass roof drastically reduces the flat metallic area for a magmount antenna, it does not block RF either. Since the only place for a small magmount is above driver's head, the antenna cable would be in the way of the passenger because I don't leave the antenna outside when the car is unattended, go figure. But there is plenty of space in the back of the car. Yes, inside, but with all those transparencies (be it glass or plastic), RF-wise it is almost like being outside.

The plan is to place the magmount base on a metallic surface and let it rest on the parcel shelf. At home I found an L-shaped 40 cm long iron piece that can be forced between the back seat and the shelf. SWR of this combo is 1.5:1 on the FT-817. So far so good.

Will it work?

06 September 2018

Nagoya UT-106 intermittent signal

Now that I was enjoying trouble-free mobile HAMming, my modified Nagoya UT-106 developed a fault causing intermittent reception. Moving the coax near the RTX would restore/loose the signal, so probably something has broken in the coax. Since the handheld lays on the passenger's seat, holding the microphone causes it to move around and put some stress on the cable.

I will cut out the broken part and try to resolder the SMA connector. Before that I will fit a PL-259 so that I can try the whole setup with a more powerful RTX as well as measure SWR.

03 September 2018

FM radio for the morning routine: September 2018 attempt

Following my previous post on two attempts at joining the morning news and the morning bathroom routine, in both cases something is too wrong. Memory lost and instable signal are no-go.

Initially I admitted my failure to provide a suitable device and let the family member head to the shop to look for a replacement. Then an idea strike: why not use the FM radio into that old Samsung Galaxy S phone that was gathering dust? Just fit a 3.5mm jack (with enough wire) to behave as an antenna and set the output through the internal loudspeaker.

Bingo! While an overkill, it is battery powered, rechargeable and does not loose memory when the battery goes flat (but you can monitor it easily). It has more than enough audio power to fill the bathroom and costs nothing. Last but not least there is a self power-off setting at 30 minutes! The only drawback is that the RF-GSM part has to be ON to receive FM radio. But that works even without a SIM card inserted.

As shown in the picture, if the FM station is close/strong enough a 3.5mm jack alone acts as a perfect antenna (picture shows a 5mm to 3.5mm adapter). Probably it also helps not to overload the input stages resulting in better reception!

Let's see how long this solution lasts.

Note. I know I could have used an Android app to listen to the Internet streaming transmission. But who knows if there is still a working app around for Android 4.x? And how it would compare with power consumption? And the current over-the-air solution works even during power outages.

01 September 2018

FM radio for the morning routine

The "old-style" replacement RX-16F
I was appointed an apparently simple task from a family member: have an FM radio in the bathroom to listen to the morning news. It is basically a single frequency FM receiver outputting audio through a loudspeaker. Possibly as small as possible and requiring as little maintenance as possible. Something: "flip a switch and listen to the news."

If we were in the 1980's I would buy an analog tuned pocket radio powered with two AA batteries. Unfortunately they don't seem to be produced anymore, replaced with energy-hungry digitally tuned radios (with a varying degree of user friendliness user interface). Used devices have all sort of problems.

4 years ago I bought a small cube powered with a rechargeable Lithium cell (Kevler KP-520PLL). It would receive FM just fine with a big problem: current consumption. Even when powered off it would drain the battery flat in a week (2mA when off, 48mA when on). What is worse is that it looses memory of the last tuned station when the battery dies and the single-button tuning system makes it really annoying to reset way too often.

Then in Marzaglia ham flea market in May 2018 I picked a 1970's analog tuned FM radio that sounded good in the field, marked RX-16F. This one, while lasting forever on a couple of modern AA batteries, suffers a long forgotten (and solved) problem: the hand proximity effect! If you hold the receiver in your hand it would behave perfectly, but looses the tuning and strength (no AGC!) when left on the table. It's fine for listening to the football match while walking downtown, but not practical for the bathroom morning routine.

I need a better solution.

Back of the FM radio.
RX-16F circuit.