View Full Version : REDSUN RP2100 HAS IF OUT?
New double conversion PLL synthesized receiver on ebay (vendor lipyn) for US$56.90 + $38 shipping with "AM IF Output for Expansion of CW, SSB, DRM". Here's a search link: http://search.ebay.ca/search/search.dll?from=R40&satitle=redsun+rp2100.
Many internal pictures here: http://www.hongsedianbo.com/radio_doc/01.asp and periodic updates on availability and features of this and other Redsun models at: http://www.radiointel.com/.
This may be a much better bet than the Kchibo KK-DRM01 which has a low 450kHz first IF.
Tom
But having to pay another 2/3rd of the price for shipping is annoying.
An RP-2000 (export model) with english labels should also be available.
Roland
I ordered one just for fun and it already found its way to Frankfurt. But I can't get any signal from the AM IF output jack:confused: The reception seems to be very good, but there are quite audible distortions in the bass frequencies on AM and FM. The FM Tuner has no problems with many strong signals, even not if connected with cable TV.
But I can't get any signal from the AM IF output jack:confused:
Somewhere else, I have read that the audio output jack also seems to be a bit problematic on this receiver and some people only get a proper contact, if they pull the plug out a little.
Or does it perhaps deliver 455 kHz out and not 12 kHz?
On the other hand, there is a 4066 being shown on the chinese webpage hosting the pictures of the interior of the receiver. This could well be the second IF mixer.
There is one big disadvantage which all these chinese receivers usually have: It is almost impossible to get a circuit diagram for such a receiver, quite unlike for a japanese or Taiwan-made receiver. The chinese manufactureres seem to be quite afraid of other competitors (most likely other chinese companies) copying their designs, perhaps not without reason and they keep their circuit diagrams secret.
Roland
Hi Roland,
I just connected the AM IF output from the RP2100 with the external antenna input of the Degen DE1103. And on 455 khz I get a clear and strong signal with the station that is tuned on the RP2100. Indeed it is only a 455khz IF output. So I need an additional mixer to test DRM capabilities....
BTW The bass distortions are gone now. I think the switches are of very low quality. So the sound is very good and loud. It might be a very nice office disco :D I haven't got any problems with the earphone jack so far.
It runs with 220V /50Hz or 4 D Cells or 4 AA cells or 9V DC, quite a lot of options. Large display, 10 khz or 100khz tuning steps on FM and 1/5/9/10 khz steps on AM. Also a RF gain control and a DX/local switch. External antenna conectors for FM/SW and MF.
I only miss the longwave band.
So I need an additional mixer to test DRM capabilities....
Hi Carsten,
I have a small box with a mixer and filter for 455 kHz inside, that you could use for testing, maybe next week?
Simone
So I need an additional mixer to test DRM capabilities....
Time to build an IF mixer on your own, eg this one (http://www.dl5mgd.de/drmmischer/drmmischer.htm). It's easy!
I only miss the longwave band.
There are no longwave stations in China. Since you have most likely bought the chinese and not the export version of the receiver, you can't expect it to receive longwave. But there is a chance, that the longwave band can perhaps be activated inside the receiver by adding or opening a wire jumper or by putting in an extra diode in the circuitry around the PLL chip. There won't be an input preselector for LW then however but it might work somehow at reduced performance.
Such a move would however require close inspection of the PLL circuitry, especially the chips used.
Does the receiver have chinese lettering?
Roland
@ Simone
No problem, thanks.
@Roland
Yep, it is the chinese version. The coolness factor is much higher with chinese lettering:cool:
Here are some photos, only from outside. On the backside you can see the AM IF output jack, it is an ordinary radio/tV antenna jack. Same is for external FM/SW antenna. External MW antenna is between them.
http://home.arcor.de/carsten.knuetter/rp2100_1.jpg
http://home.arcor.de/carsten.knuetter/rp2100_2.jpg
http://home.arcor.de/carsten.knuetter/rp2100_3.jpg
http://home.arcor.de/carsten.knuetter/rp2100_4.jpg
Today I got the mixer from Simone and tested DRM with the RP2100 this evening. I just connected the AM IF out with the mixer and the mixer with the soundcard. It works! It will not be a new SNR highscorer, but it made very stable reception on 7320 and 3995. The spectrum looks not perfect at the right side, but no effect in the SNR spectrum. But Notebook must run on battery, rp2100 must run on battery and distance between notebook and rp2100 should be a maximum. Both logs are made with telecopic antenne of rp2100 and rp2100 was near balcony for 7320 log and on balcony for 3995 log. The dropouts in the middle part of the 3995 log were caused by the powermangement of the notebook.
Nextime I will try the Degen DE31 loop antenna with the rp2100.
That is the spectrum of 7320 khz.
Hi Carsten,
since - at least in my experience - the achievable SNR usually falls with increasing frequency with this kind of PLL circuits, it would be interesting to see how high an SNR can be obtained at the highest possible frequency. Can you give it a try on 15440 or 15780 kHz? Or perhaps even on 26000 kHz in case it should be open by chance?
Two other things that would be interesting to know:
- Does the level stay constant and is the AGC effective or do you have to adjust the levels occasionally?
- Does the bandwidth also change on the IF output when you switch between both filters, so is the IF tapped off before or after the IF filter?
Roland
Hi Carsten,
I just ran the chinese webpage with the pictures of the RP2100 through a chinese-to-english online translator and I found that the author's RP2100 exhibited interference from the processor's clock signal in the range 18 to 22 MHz whenever a button is pushed (the translation is not very clear in this respect). There was a response from the manufacturer and they recommend a modification according to this picture (http://www.99free.net/myfile/redsunlele/2100-20m3.jpg). This is a 10 nF ceramic capacitor.
Here is the text of the (badly) translated response:
Thank you to purchase our RP2100, in yours use to discover 18-20M has the quite big clock disturbance, we in the trial manufacturing and the production process had not discovered you said phenomenon, but engineer the parallel 103 porcelain piece electric capacity may improve this phenomenon in yours discovery foundation on the C114 electric capacity, because you have extremely well begin the ability, please help to experiment and to confirm whether may improve this phenomenon which you said. Extremely thanks!Attaches the schematic drawing, please search and collect email:hhy@pub.meizhou.gd.cn
Or here examined
Schematic drawing: Http://www.99free.net/myfile/redsunlele/2100-20m3.jpg
The link given is the same one as the one which I already gave above.
Roland
- Does the bandwidth also change on the IF output when you switch between both filters, so is the IF tapped off before or after the IF filter?
Roland
Yes, the IF bandwidth does change when I change between the 2 filters.
Higher will follow maybe at the weekend.
I didn't change rf gain manually during the logs. It is alway at maximum as suggested in the manual.
I didn't change rf gain manually during the logs. It is alway at maximum as suggested in the manual.
This may be a good recommendation in the majority of cases when using the built-in telescopic aerial, however it certainly isn't in case an external antenna is used.
In case of an external antenna, with the exception of a tuned antenna such as the Degen loop or an external preselector, there will be intermodulation products and you will have to reduce them by reducing RF gain or by setting the switch from "DX" to "local".
Roland
here is a log of from 11640 Sines. But this frequency has got very strong interferences from both sides, so the result does not say much about the rp2100 capabilities.
Here is a log from 5980 khz. For this transmission I had to reduce the rf gain. At maximum gain, Dream lost synchronisation every few seconds. DRM SWR had a permanent red audio LED, but perfect audio.
Somewhere else, I have read that the audio output jack also seems to be a bit problematic on this receiver and some people only get a proper contact, if they pull the plug out a little.
Hi Roland and all,
Perhaps the "bad contact" problem is the same as in the Kchibo KK- DRM01: The 12 kHz IF jack is a stereo jack ( :confused: ). If you insert a 3,5 mm mono plug, the the 12 kHz output will be shortcircuited to ground as the L + R poles are connected in parallel in the Kchibo.
True, if you pull the Mono plug out a bit, you get signal, but the best solution would be to use a stereo plug wired for mono operation.
Terje
A few khz higher (13790 khz) looks still quite ok....
And here are a few more details from Dream. RP2100 was tuned to 5980 khz. What you can clearly see is, that the SNR is limited somewhere inside the radio and not by reception conditions. If I have the same input spectrum on my aor, the SNR spectrum would look nearly the same as the input spectrum. On Rp2100 SNR is quite a flate line. But who cares, it really does not matter if you get 100% audio with 20dB or 30dB.
rp2100 scored with 23.4 dB tonight on 1296 khz.
rp2100 scored with 23.4 dB tonight on 1296 khz.
How about Vatican Radio on 1611 at the moment?
I had expected more than 23.4 dB on 1296 kHz. I guess there is still room for improvement by increasing the AGC time constant or by filtering the AGC voltage a bit better.
If there is no dedicated external AGC circuit, then the AGC lowpass filter is made up of an internal resistor and an external capacitor that is connected between pin 11 of the LA1260 IC and ground. Sanyo, the manufacturer of the IC, uses a value of 10 uF in its application circuit. Since the capacitor is most likely of this value in the receiver as well, enlarging it by adding 22 uF in parallel might be worth an experiment.
Roland
Hi,
this morning I tried the 15440 khz with the redsun. Perfect results with the telescopic antenna. Sometimes I had to adjust the RF gain. Not really nice, I`m not used to that from my AOR. However it played constantly Deutsche Welle with good quality.
Hi
In last 15440.png
DW Sat Jul 09:01:00 2006
Input Spectrum low level average about -120dB
hight level average about -80db
(difference average about 40db)
good signal and no interference
but SNR average only about 20db
Why? Where disappear 10 .. 15 Db ?
Is it PLL phase noise ?
Not visible interference from computer?
Antenna ? Mixer or IF or IF filter?
Sound card ? Low freq amplifier ?
I compare with
direct conversion receiver with quadrature output
http://www.smail.lt/~ncss/regen_info/7295_IQ_interference1.jpg
Input PSD low level average about -110dB
hight level average about -85db
(difference average about 25db) and
big symetrical interference
but momenticaly SNR about 24Db
and last
http://www.smail.lt/~ncss/regen_info/7295_IQ_25Db_from_dif_30Db.jpg
Input Spectrum low level average about -115dB
hight level average about -85db
(difference average about 30db) and
small symetrical interference
and history SNR average about 24db
Best regards, Saulius
Simple DC_IQ + ICF7600G & IQ_Mixer_EF86 & Q_multiplyer_autodyne_EL86
Sometimes I had to adjust the RF gain. Not really nice, I`m not used to that from my AOR.
This is due to the limited AGC range of the receier. An IF level that is still 20 dB above the noise in Dream's input level window is usually sufficient and it is better to let the level decrease that much during fading than to increase RF gain and risk degrading reception because of bad intermodulation performance. This applies especially when external broadband antennas (wires, untuned loops) are used and especially in the evenings when signal levels from 5 to 9 MHz are very high and when there is a high probability of intermodulation in your receiver.
Often, you can determine the point at which broadband intermodulation sets in by tuning the receiver to a clear channel and advancing the RF gain. At a certain setting of the RF gain, there will be a sudden increase in background noise (like several stations above each other) in which often no particular station can be identified. It is very advisable to stay well below this point, otherwise one risks degrading DRM reception. Unfortunately, this sets a lower limit for weak DRM signals.
Roland
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