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If you need a small FM transmitter and have a cavalier attitude to spectral purity then it’s easy enough to use a Raspberry Pi or just build an FM bug. But this project opens up another option and gives a chance to experiment with a fascinating chip. Pokud rádi lovíte stanice na dlouhých vlnách, na XH DATA rovnou zapomeňte. Je tam naprosto hluchý. V pásmu majáků kolem 400 kHz už je to lepší, a na středních vlnách zcela bez problémů. Lze však říci, že Tecsun PL-660 je na středních vlnách o něco citlivější, což může být dáno delší feritovou anténou. I have held the call G3SBI since 1963 and a year or so afterwards I bought two AM handheld walkie talkies designed for the USA 27 MHz citizens band.They were not really legal over here but I was keen to see what range could be obtained.Although the receiver was a superhet the best I could do in a built up area was about 1/4 of a mile. In the old days ICs were pretty general, but as they became more specific there were often limits. When AM stereo was trying to take off, I remember looking at an adapter in Radio Electronics, using a Motorola IC and realizing it was almost what was needed to make a sideband selective synchronous detector, but one stage might affect it’s use for that. It wasn’t clear, though much later I read that Sony used an AM stereo IC to bet the function in their famous 2010 shortwave receiver. I) Amidon 7.5” x .5” ferrite rod, part no. R61-050-750 (MW model) OR part no. R33-050-750 (LW Model), available at http://www.amidoncorp.com/rods-and-tiles/
When your Litz wire lead ends resemble the photo above, cut the soldered portion down to a length of 3/16” (5mm) and observe the appearance of the end of the Litz wire. It should have a bright, solid circular shape, with no gaps or individual Litz wires showing. If not, reheat the end of the Litz wire while adding some solder, and repeat this step. The Si4735 DSP chip has markings of “3560, DCUL, .738” and provides a wide range of AM bandwidth choices for the Medium Wave DXer (6K, 4K, 3K, 2.5K, 2K, 1.8K and 1K). These perform very well, and as with the other DSP-enhanced portables, the narrowest bandwidth (1K) provides the most sensitive AM band reception. It also depends on what you want. If you do everything in a computer, you just need a quadrature oscillator and a pair of mixers for receive and another pair for transmit (and any receive and transmit amplifiers. That’s not as simple as a magic IC that does it all, but it’s simpler than building an SSB transceiver. Ačkoli jsme ktomuto rádiu přistupovali sjistou počáteční nedůvěrou, dopadl tento ryze čínský pokus překvapivě dobře.A valid product review is one where you have experience or knowledge of the product that you would like to share with others. I remember about 20 years ago, I was on the mailing list for one IC company and there was a string of intriguing cellphone ICs. Wait, it was Maxim, and they offered samples. I kept looking at those, knowing they had a lot of what was needed for “SDR’, but it was never clear from the bits they sent out whether they were too sculpted to cellphone applications or they could be shifted to “useful” frequencies. The D-808 is shipped with a non protected button top 18650 battery with a 67mm length. The protected kind averages 69mm in length and have a conducting strip for the protection circuit board attached at the negative pole. Pod displejem se tradičně nachází klávesnice. Má velmi malý zdvih, avšak je spolehlivá. Pokud jste zvyklí na poslech v posteli, kdy vedle dřímá drahá polovička, jemné cvakání kláves ji rozhodně rušit nebude. Zatímco všechny jmenované přijímače byly superhety, XH DATA je rádio čistě počítačové, tedy přesněji SDR. Rozdílu si všimnete na první poslech. Šum mezi užitečnými signály je jakoby zaprskaný, zatímco superhet má šum hladký. Druhým znakem všech levnějších SDR přijímačů jsou nepatrné pauzy mezi jednotlivými ladicími kroky. Počítač uvnitř se zkrátka musí přepnout zkanálu na kanál. Působí to zvláštně, nás to trochu štvalo, ale zvyknete si. Tento drobný nekomfort vám vynahradí velmi dobrá citlivost rádia.
Refer to the photo below. Using the previous procedure to install shrink tubing (which is described in the PL-380 transplant article) install a 2.5” (63mm) length of shrink tubing over the two Litz wire ends, and shift the shrink tubing into the position shown in the photo. After this is done cut the two Litz wire leads to the lengths shown in the photo (NOTE: make sure that the ends of both Litz wires are cleanly cut, not frayed and at the minimum diameter before attempting to insert them into the shrink tubing. The process is much easier when the Litz wires pass smoothly through the shrink tubing). To set it all up i first tuned the PA into a 50 ohm load and then inserted an SWR bridge between that and the parallel tuned circuit/series tuned link and adjusted the two capacitors to get 1:1 SWR. Products to be reviewed typically should be tangible ham radio related items such as radios, antennas, towers, test equipment, feedlines, etc.
The XHDATA D-808 has multiple display functions, which can be toggled by the indicated key. The first option is the temperature in either Centigrade or Fahrenheit (depending on your pre-set preference), while the second option is the alarm time. The third option is the current time (which you need to set according whether you prefer UTC or local time), while the fourth option is the received signal strength in both dBu and dB. Refer to the photo below. Lay the two cabinet sections down flat as shown, ensuring that the Litz wire shrink tubing is in the exact position shown (if it isn’t, carefully slide it along both Litz wires until it is in this exact position). Carefully thread one Litz wire end through the empty wrist strap hole, then thread the other Litz wire end through the hole, as shown. Finally pull on the two Litz wires together from the right while guiding the end of the shrink tubing into the empty wrist strap hole, and pull a short section of the shrink tubing through the hole (as shown) to protect the Litz wire insulation from friction damage.
More Info: https://xhdata.com.cn/collections/xhdata-hot-selling/products/d-808-radio?variant=43660713558334 A lot of ICs offer two mixers, and a quadrature oscillator of some sort, but can you easily shift the frequency down to more useful frequencies? The SI go in the other direction, certainly useful for shortwave, but can they be programmed for various modes, or are they “hardwired” for specific modes. I get the feeling modes and selectivity are adjustable, but from between some preprogrammed modes. So even if you attach your own controller to a Grundig G8 portable’s SI IC, you can get more bandwidths but no SSB. Na dlouhé anténě (cca 25 metrů) se XH DATA během dne chová dobře. Vnočních hodinách má sklony se zahltit, což není nic překvapivého.My XHDATA D 808 as received on FM covered 88 to 108 MHz.However I persuaded it to cover 64 to 108 MHz so that it covers our 4M band.Unfortunetely the firm ware doesn’t allow you multimode reception between 64 and 108 MHz and the tuning step options would be useless for receiving for receiving CW on 4M. Thank you for sharing this technical overview of the XHDATA D-808, Gary! I’m looking forward to the antenna mods you’ll no doubt make to this compact DX machine! However in the transceiver chip if it could generate multimode between 64 and 108 MHz it would be easy to have a HF add on with only a mixer and a 50 MHz LPF. The supplied 3.7v lithium ion battery has superior run time, and may be easily charged using the supplied USB cable to either a computer or AC outlet (with the appropriate adapter). As reported in various posts throughout this year, the D-808 model has rugged construction with an excellent record of survival under tough conditions, including hot summer days, moderate rain exposure and extended usage as the main receiver during a 9-day ocean cliff DXpedition in Oregon—performing flawlessly at all times. Conclusion
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