Pain in the butt: chinese car radio has bad fm reception/mixes channels - Page 1
Forum section: electronics / beginners

author: epigramx
author_rank: Regular Contributor
timestamp: August 19, 2019, 08:48:51 am
content: It's the one you find for ~$12 when you search car radio in aliexpress (i.e. i.imgur.com/H7sFoD6.png). Impressive for the price, full speaking bluetooth support and all so it can make an ancient car feel better for almost nothing.But, my dad cares about good reception but this one seems to lose channels relatively easily. It's like it sounds good when it's stationary but when the car moves, every few seconds it hisses/loses reception/mixes channels for 1-2 sec.Any chance to fix that? It's also a consistent problem with their design, since most people report the exact same behavior (fine on other features, crap at fm radio reception).

author: snoozer
author_rank: Contributor
timestamp: August 19, 2019, 01:28:13 pm
content: Hello,I am wondering, could that have to do with different requirements of channel spacing (is it called that) ? I have read something about a 200kHz spacing in the US (maybe other countries) and 100kHz spacing in EU or something like that. Maybe there is a hidden function to adjust the radio for different regions.https://en.wikipedia.org/wiki/FM_broadcast_bandRegardsJan P.

author: Audioguru again
author_rank: Regular Contributor
timestamp: August 19, 2019, 02:00:31 pm
content: You get what you pay for.The cheap Chinese FM radio might be a simple "crystal radio" or a horrible "super-regen" design.A properly designed FM radio has excellent sensitivity but also has automatic gain control to tame very strong signals, and has good selectivity so that it does not mix channels.Maybe the cheap radio does not have a good signal limiter to properly "capture" the signal, then it has severe interference from multipaths.

author: amyk
author_rank: Super Contributor
timestamp: August 20, 2019, 12:26:14 am
content: Open it up and post detailed pictures of the insides. If there are circuit boards, preferably both sides.

author: radiolistener
author_rank: Super Contributor
timestamp: August 21, 2019, 07:36:37 am
content: Probably this is because it uses cheap FM receiver, which cannot keep good reception in unstable RF environment.If it has bluetooth, you can try to connect it with your mobile phone and use FM receiver from your mobile phone.Just attach antenna into phone jack of your mobile phone:https://www.aliexpress.com/item/32829125269.htmlYou can also buy Chinese charger for car, it will helps to avoid discharge of your mobile phone.https://www.aliexpress.com/item/32875782040.htmlIf you planning to use your mobile phone as FM receiver, here is also Chinese car phone holder:https://www.aliexpress.com/item/32616510759.html

author: kjr18
author_rank: Regular Contributor
timestamp: August 21, 2019, 09:04:43 am
content: I bet inside will besomething like this radio module

author: Psi
author_rank: Super Contributor
timestamp: August 21, 2019, 09:30:49 am
content: *Might* be able to fix it by changing whatever IC it's using for FM radio with an original IC.eg, it might use a FM radio IC that is a china clone of a proper brand IC. That stuff happens a lot in china.However, thinking about it more, i suspect what they are likely doing is using a cheap combination bluetooth+FM radio IC to save money.Basically a BLE chip with a bad FM radio hacked onto the radio section.You wont be able to change that as the BLE radio comms will be very integrated with the OS/MCU.You could perhaps open it up and make sure the antenna section has coax to the external antenna socket. Maybe it's just wires?But best option is probably just to buy a new different $20 one that doesn't have this issue.It will likely have some other different issue though

author: SparkyFX
author_rank: Frequent Contributor
timestamp: August 22, 2019, 06:11:33 pm
content: Quote from: epigramx on August 19, 2019, 08:48:51 amAre all antenna connectors OK? Does shaking or moving them cause the same problem?Some cars have a preamplifier near the antenna, which requires supply power.Snoozers point of channel spacing might also be an issue, so which frequency range does the unit support and in which spacing and where do you use it?

author: janoc
author_rank: Super Contributor
timestamp: August 22, 2019, 06:15:57 pm
content: Quote from: Audioguru again on August 19, 2019, 02:00:31 pmUmm, for FM? I don't think so ...More likely than not it is using a cheap FM radio IC and/or poor antenna connection. The constant signal dropouts certainly point to the issues with the antenna. Either the connection is bad or the device is poorly engineered and has very poor sensitivity (assuming there is a decent FM signal nearby, of course - i.e. don't test this somewhere in an underground garage!).

author: Audioguru again
author_rank: Regular Contributor
timestamp: August 22, 2019, 06:27:03 pm
content: Quote from: kjr18 on August 21, 2019, 09:04:43 amThe TEA5767 radio module is missing all the important parts of arealFM radio. it will have poor sensitivity but will be overloaded by strong local stations and its poor selectivity might pickup a few stations at the same time.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 22, 2019, 11:52:49 pm
content: Quote from: janoc on August 22, 2019, 06:15:57 pmYeah, it is not uncommon to use a very inefficient antenna with an amplifier at its base, the power to the amplifier being fed through the coax.My daughter's old Daewoo had this setup, & the connection was brought up through the rear tailgate for some unknown reason, with a section which had to flex, losing the shield after a while, so the amp was "dead".(they didn't leave any slack so you could fix it, either).The "antenna" now consisted of just the piece of coax, which, strangely enough worked OK "sometimes"!