Tuesday, November 3, 2020

Bolong radio HS902


Bolong radio  HS902

THis article mirrors here from my old page of geocities that will very soon be deletd dur to Yahoo's proposals :(((

Bolong radio is the oly analog radio of the picture  with enhanced view ( ie at the left)

Aug 31, '09 9:57 PM
for everyone   http://zlgr.multiply.com/reviews/item/92

 This radio has been the results of a replacement project with a Chinese friend who lived for a short time in the student residence two years ago. He used  mainly that   radio in offer to listen a  bit to the local radio  stations but also  his homeland.

I  give to him a  Kchibo model found from  the local market mainly the 515  which is a semi   digital , ie having a digital readout but is  fully frequency agile. More information n this radio you will find on the  chibo.pdf file along with some interesting technical info also for Bolong.

Why I am writing this report , though  I have already written in the  pdf? This is because with the return of the PL200  back to the factory for servicing or replacement  - a total of 4  weeks – and the  C330 already given to my father in the  country house , using  big  radios as 1102 and 1103  in the road  is quite  uncomfortable, requiring the  use of cassette sized radios only in the chest pocket  of the blouse which is mostly preferable for me. All that time I had the opportunity to use and test it more than previously. I also like to listen to the music when I am walking inside the city. And it impressed me very much with its audio fidelity. 


The radio is  a bit thick-y  with  black  color and metallic mesh surface over the  speaker . I never use it as I prefer to use  my  earphones . It is a also relatively heavy compared to the C300

 There are three buttons on the front face:  ON button for FM one for AM , one stereo  switch and onle lock switch all locatd on the bottom right position below the  display . ON the top there is a 8  band sliding switch . ON the left there  is a volume control a  ON off switch and a earphone connector.

There is a stereo FM light and a band light( FM or AM ) and a tuning light on the top right  position.

The thumbwheel is relatively small for my fingers at 1 cm of diameter and a little hard to turn . I prer it this way   so that it doe not tune out for any reason .




The specified coverage  shown in the display are  




My measured (approximate)


 6.9- 7.4

5870- ~6550


9.45 – 10

9.400 -10.100?


11.6- 12.1




15000- 15800


17.55- 18.










85.4 – 109.5(presume)


Here are my comments:

The MW band  in its specifications are for 531- 1620 kHz  but as it is a  analog radio its freq span is quite wider . I have heard stations on the upper MW  band   up to  abt  1670 kHz where  I can listen to the Greek pirates mostly QSOing at early to late nights and at least  3-4 channels  below the 530  band ( vacant freqs  every times  I tested)  


ON FM band  it is the same. About  1-2 MHz  below and 1-2 MHz  above the band. These extended freqs were totally vacant . Using fully unfolded antennas Bolong shown two very poor images of 107.5 and 106.8 – at its lowest  used frequency tht means 85.4 is the lowest freq

The radio has also  a FM stereo /mono switch and a  lock button. It’s LO  seems  more stable  than SW

ON the SW bands it is a  bit  difficult to determine   the accurate frequencies  especially due to  high LO drift.  

I have an example here:

ON the 17 MB band  , I can listen to 17490  kHz China Radio Intl in English  service  local morning to midday times at the start of the  tuning band  The signal is excellent   so that  with just erected antenna I can listen it as it was local . . However   the local oscillator   drifts   to a great extent so that CRI sometimes is inserted  in the band  or even is lost outside the dial. I can assume that the LO  can drift about  30 kHz  above or below  its main frequency!!



This is a  all stage transistor radio . as the radio , is a hard used  model by the Chinese student  I found that that  the there are several dropouts with the  sudden moves or light shocks in my pocket  That possibly means  soldered points  are loose. In several light shocks and  during Sw listening  the  radio was reset  to the default  FM band.


Audio  fidelity:

  • FM : One of the  best sounded radios on FM   with extended  fidelity and trebles  over any other radio  including the stereo system of my wife! . Using good and high quality  earphones / headphones is a pleasure. I have the same impressions of using the Degen 1103 earphones (un-sponged ) and AKG UR20  headphones ( both of high audio response)
 Diversity testing  with De1102  and same earphones in both radios show same bass  response and trebles moving towards Bolong .Also  audio is more pleasant than DE1102
  •  AM Modes Good  audio  quality reminding me  the audio my old RT430 SILVER  radio tape recorder ( transistor made)  has.

Earphone Audio level : Quite high level . Just a little audio level  can overdose the earphones. In contrast , audio output is very low .Same happens with  the earphone level  of C300 and PL200



  • FM:  A little better  than 1102 . I could listen to NET 88.0  with less QRN than 1102.
  • MW :  Its   MW sensitivity is  low to very low  . Stations with good signals in  other radios  as R Skopje  810  is heard poorly in Bolong .During the nights this is a little out of question ! 
  • SW :   Parallel (earphone diversity ) testing with  R75  shown a sensitivity level same or better than De1102  In a table below  you will see  that I several bands  Bolong radio has better sensitivity or resulted audio than 1102




  • FM:  Fair levels . Good (?)levels of AGC/AFC  can off tune  to an stronger adjacent station during walking… Several stations  that  1102 can listen , Bolong can’t  especially  lower signals in our  crowded bands
  • MW : 9-10 kHz Adjacent stations  are not interfered ( except of producing QRM whistles )
  • SW : About 10 kHz  ,Near to 1102’s  level except in  near  very strong adjacent signals that cover several 5 kHZ channels.


Battery usage: 

The radio uses two AA batteries as most radios do today. As it is  analog radio it  has very low power usage  . The batteries I put 1 years ago  have ended recently . I can assume more than 100 hours of usage

 Here is a list of  tests with Bolong and DE 1102 using the diversity earphone stereo  method  ( 2x 1102 earphones)

 Bolong >>> 0   DE1102 >>> 9 








































As in result  in most bands Bolong seems to  have a better  sensitivity  or total  audio result  than 1102 except the 50 mb . ON 50 mb there were superhet images  from  the lower part of the 41 mb that mixed with the upper part of the 60mb stations ( 6200 and up)

You read my review. This is a result of more than 10 hours  of testing usage. 

Addition 2020  :

To notice  , the radio has been under problem after 2018 and was used occasionally since then only fore testing hedphones and in ear phones while one screw was loosened makingf the radio lose contact with its board . the technician tried it by using some glue and isolated the usage of all buttons for bad,

I have given that to another electronics engineer  who rejected to service it as no spare materials exist



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