Radio, Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器

http://wp.me/ph3BR-1HZ

 

一個瑞典人的網站, 2001年後就沒有更新, 有些很特別的資訊, 例如無線電或收音機裡面的中頻變壓器的歷史資料和使用方法. 雖然是舊有的資訊, 不過現在還是適用, 除非玩 SDR, 最近翻看, 結果它的網站搬家了, 舊的資訊找不到, 唯有試試看 WEBARCHIVE, 找回來這頁, 存起來看看, 除了錯別字以外, 所有資訊及版權歸原網頁或作者所有 (SM0VPO)

最重要的是它給出了中週為什麼要使用中心抽頭的原因和原理. 頻寬是圈數比的平方反比例, 意思就是, 窄頻和高選擇性, 只通過或接收 “單一的頻率"

http://web.archive.org/web/20120327094301/http://hem.passagen.se/communication/ifcan.html

 

 

——copy of http://web.archive.org/web/20120327094301/http://hem.passagen.se/communication/ifcan.html

Declaration : all those information copied here (blow) is for reference only, the original author (it is believed SM0VPO, the call sign and own those material and perhaps abandon a website only but not to neglect the copyright of those information). Those information presented here is slightly edited with errata and illustration re-rearrangement.

 

IF-CAN (Intermediate Frequency CAN)
This side presents some facts about IF-CAN (IF-transformer).
All contribution to this page are most welcome

Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器

 

Background
These transformers are specially designed tuned circuit in RFI-tight groundable metal packages for narrow bandwidth IF application. They are called IF cans. As shown in the 1968 specification sheet of figure at right,

Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器

this unit includes a 125-pF capacitor, and the arrow between primary and secondary. An arrow  indicates that the tuning is attained by tuning-tool (a non-metallic screwdriver) adjustment of the ferrite core (slug). The purpose of the primary winding tap is to increase the effective Quality (Qeff) of the collector circuit in the narrow band IF of the standard broadcast receiver.

Each IF transformers has self resonances with an impedance max at predefined frequency. The resonances frequency can be adjusted by turning the colored ferrite core. In an ordinary radio, you will most often find 4 types of IF-cans.

For the FM part the IF frequency is 10.7MHz. The color of the slug in this CAN is most often pink.

For the AM part the IF frequency is 455kHz.

RED – Oscillator. With 30pf – 300pf = 1MHz to 2MHz
YELLOW – First 455KHz IF filter transformer
White – Second 455KHz IF filter transformer (not always used)
Black – Last 455KHz IF filter transformer

 

How to connect the IF transformer?

Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器

The IF transformer uses a tuned primary winding of typically 110 – 160 turns of wire with a 180 pf – 200 pF fitted across the coil. This winding is usually tapped at about 20 – 25% and connected to a centre pin. Unless you have any data on the coil then it is debatable from which end of the coil the tapping is made.

Impedance

Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器

The diagram above shows the impedance as function of frequency. The phase angle is also plotted. The ferrite core (slug) is yellow 455kHz. As you can see from the diagram the Impedance has a maximum at the resonance frequency. At the resonant frequency the phase is zero and the impedance is pure resistive.

Primary winding tap and Q-factor

Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器

The schematic above show the IF-transformer. RT is the resistance in the amplifier stage.

For instance, suppose the tap is not used. The equivalent circuit is (figure at left), of course,

Qeff = RT/XL and the bandwidth BW= fo/Qeff.

IF the power supply line (ac ground) is connected to tap point, the resulting equivalent circuit is that of figure right.

Here, L1 + L2 = L, so the circuit is resonant at the same frequency. However, since L is proportional to N^2, where N is the number of turns for the inductor

XL2 = n^2 XL where n is the turns ration defined by the tap point n = n1/(n1+n2).

Ignoring finite inductor Q, the effective tapped circuit Q is QT = RT / XL= RT / (n^2 XL) = Qeff / n^2.

Since n<1 ,QT> Qeff of the untapped transformer.

EXAMPLE
RT=2500 ohm
XL=500 ohm
Determine the Q of the two circuits. The tap point is 1/3 of the inductor turns from the bottom.

Solution
Qeff = 2500 / 500 = 5
XL = n^2 * XL2 = (1/3)^2 * 500 = 55.5 ohm.
QT=2500 / 55.5 = 45
The Q has been increased by 1 / n^2 = 9 times.
The bandwidth is 1/9 of the untapped value.

RULE: By tapping the transformer the Q-value increase and the bandwidth decrease.

What is inside the CAN?
The two pictures below explain the inside of the CAN.

Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器
Intermediate Frequency CAN, IF-CAN, 中週, 中頻變壓器

 

 

Declaration : all those information copied here (above) is for reference only, the original author (it is believed SM0VPO, the call sign and own those material and perhaps abandon a website only but not to neglect the copyright of those information). Those information presented here is slightly edited with errata and illustration re-rearrangement.

 

——copy of http://web.archive.org/web/20120327094301/http://hem.passagen.se/communication/ifcan.html

廣告

Tube Radio Feilo ShangHai 飛樂 261-11

http://wp.me/ph3BR-1DQ

 

這個祖國1966年出產的收音機有意思, 印繁體字的, 壞的肯定不響.

到底上海話, 飛樂  = FeiLo ?

FeiLo Tube Radio
FeiLo Tube Radio

膽機, 純膽收音機, 電子管機, Tube Radio 就是它.

老東西了, 壞的, 客官們問說要來幹嘛!? 花時間在有價值的地方才是. 老婆老公年紀大了壞身體了, 拋棄另覓新款, 花時間找個幼齒陪玩也是 🙂

為了親手接觸電子管機, 避開那些水份和空洞的膽機美聲說, 動手做就對了. 靠的是一些素不相識的網路上的電子管機器前輩的指引, 相信這玩具定可再現風華.

基本步,清理,先能發出聲音,做到了.

http://www.crystalradio.cn/thread-781753-1-1.html

http://www.crystalradio.cn/thread-679001-1-1.html

下一步,希望收到電台廣播.

 

SONY ICF-P26, SANGEAN SR-35, AM-FM 收音機, 音質和價格無關

https://goo.gl/4pyu4f

昨天進城裡, 看到山進和SONY, 同時在路邊的店面有賣, 就買了各一個, 台幣780和740, 應該是算同樣的價了, 可能網路價有比較便宜的.

SONY ICF-P26 SANGEAN SR-35
SONY ICF-P26 SANGEAN SR-35
SONY ICF-P26 SANGEAN SR-35
SONY ICF-P26 SANGEAN SR-35

為什麼今天還有人買這樣的收音機 ? 會用收音機的和要求簡單明瞭的, 才會買這種收音機, 用過好貨的, 是回不去的, 特別是不想碰智慧手機的老人家, 聽收音儼然成了專家, 自然懂得內韻甚麼是好的收音機. 教過好幾人, ANDROID 手機可以聽 FM 廣播電台, 喇叭也大聲, 可用了一兩次就往旁邊一丟, 繼續用舊的, 理由很多個, 耗電, 難用, 忘記怎樣開關機, 充電麻煩, 不能換電池, 豎起來要另外套架子, 不小心一摔就破屏, 忘記怎樣調台, 要插耳機耳朵不舒服…………..

準備送一個出去之前, 特別比較一下, SONY 的, 低音不夠豐富, 聲音清澈, 山進的, 低音豐富很多, 相對聲音飽滿.

https://youtu.be/l1oG_JxOLPs

.

.

因此, 不論外觀設計和聲音, 都是把山進這號留給自己享用的理由, 但是 SONY 有它的獨到之處, 送人也不會失禮. 接下來可是要抽空幫人家修現用的老骨董, 因為年紀大了, 就是不要新型按鍵式的收音機. 就像看 LCD 電視常埋怨遙控器太複雜, 還是堅持用 CRT 電視, 因為遙控簡單.

上次買山進退掉的那個價格3000圓的短波收音機, 就是因為現代化的按鍵調台買來就不太聽使喚, 專家用了不到5分鐘就說, 你看…..有問題的, 試驗一下, 果真是按選台向下鍵幾次才有反應, 選台向上鍵就很正常, 每按必動. 所以這種既傳統又實在的轉輪式的電容調諧收音機有它特表的好處, 老一輩的人習慣就是愛用, 簡單易用. 看來, 年紀和習慣會有特別要求.

談到音質, 真空管收音機的音色是低音很豐富的, 這特色應該和諧波有關, 所以還在慢慢的在整理, 希望把那個1966年出廠的上海飛樂真空管收音機再次發聲, 聽說當年在祖國賣120元人民幣, 國家的補貼是20元錢, 而普通工人就45塊錢的月薪, 意思就是要起碼3個月薪水才買得到. 而據說當時都是前蘇聯的技術和零件為主, 等於今天的外商品牌 MADE IN CHINA, 不過自銷而不出口, 或者中外合資, 東芝的貼牌冰箱格力的製造. 數十年來都是這樣, 沒有看家本領就要被人剝削.

據說現在吃的差不多了, 越南, 柬埔寨, 印尼也越來越多外商去駐紮剝削. 歐美就大搞 RoHS 炭排放足跡等等有的沒的, 亞洲就競爭激烈搞代工搞生產, 燒油燒媒排出二氧化碳, 成品賣到世界各地, 資源在那幾個陸地之間搬來搬去, 其實本質上和八國聯軍搶燒了圓明園沒多大差別, 把槍砲士兵運到中國, 燒殺搶奪到的貴重物資運到歐美據為己有, 不同是被燒殺搶奪的時空/規模/國家/民族, 被包進去更多.

 

2015-12-26, 準備拆機, 想試驗自己改它的LO, 看看收77.5KHZ的行不, 拆之前搜尋了一下, 原來早就有人拆機改裝, 雖然目的不同, 但是拆來看是一樣的, 收音機都IC化了, 沒搞頭就此打住, 以後再說.

MITSUBISHI SAVRIN INSPIRE, Door Key Remote and the radio 車門鎖遙控器

short URL : https://goo.gl/THpHaj

這個時代的汽車, 一定多了一個功能, 車門鎖遙控器

savrin car, door key remote
savrin car, door key remote
savrin car, door key remote
savrin car, door key remote

一直都知道有這東西, 但既沒有汽車也不是修車的, 沒有必要不會去研究它, 也沒機會摸上手. 聽車主說到三菱打了一把新的, 舊的一把丟失了, 另外這把常常開關鎖車不靈敏沒反應, 最後完全不聽使喚. 好像要台幣1300圓左右, 原來買那麼貴…還要帶上原有的鑰匙和車主證明文件才可以配一把新的.

三菱車的鑰匙樣子就長這樣, PCB 上面的一個 IC, MICROCHIP 的, HCS200, 據說是2002年前的產品, 所以估計這個鑰匙起碼十年以上, 會壞甚麼呢 ? 裡面除了一個電路板和兩個按鍵, 另外還有一顆完全獨立的黑色小小的豆豆卡在塑膠殼的邊緣, 據說是RFID, 發車啟動引擎時就必須有她, 不然引擎會被鎖住, 好像故障一樣發不起來, 扭鑰匙會聽到發動聲音, 但是無法完全起動引擎. 所以拆的時候要小心, 據說丟失了這顆小小的豆豆, 除非有後備的鑰匙, 不然三菱會把引擎電腦換掉才能修復….真實這樣嗎? 當然除了安全理由, 應該大部分還是有商業考量.

檢查了, 花了點時間蒐資料, 劃了線路圖, 學到一樣新東西 SAW RESONATOR, TDK / EPCOS 出品, 原來高頻率的無線電, SAW 可以提供穩定的震盪和發射頻率, 不需要領牌照? (EPCOS R801 315MHZ), 另外還看了 OOK (On-Off-Keying) MODULATION TECHNIQUES FOR RADIO LINKS, 基本原理是, 震盪器運行和停止, 代表訊號0和1構成數字化的無線電資料傳輸 (會不會偷車的都這樣攔截車門鎖的遙控器訊號呢?! 沒有空深入研究, 暫時知道就此打住).

修復是比較簡單的, 清理按鈕的氧化物, 然後用自製的 milli-ohm metre 確定電阻不要過高, 一般不要超過10 milli-ohm, 因為這兩個按鍵既是電源開關, 也是選擇發射功能的開關, 看看下面的電路圖第四頁就很明白的, 電池CR2016, 2V, 20mm直徑, 1.6mm 厚度, 所以叫做CR2016, 價錢貴但是使用時間短而比較耐用, 2到3年起碼. RF震盪器的那個震盪用的晶體管換新, 不知道它原來的型號, 換上 2SC2412K, 示波器沒有能力看到60MHZ以上的, 所以測C極, 應該只看到 PWM 輸出的訊號. 試驗了, 遙控器恢復正常, 比對原廠的遙控, 距離短了一些, 不到15米, 不過算是成功修復了. 如果要深入研究, 看看 Micrchip HCS200 的 DATASHEET, 有詳細說明遙控器的編碼和燒寫方法, 第六腳的PWM 訊號輸出, 調製發射器, 輸出位於0V, 震盪器的晶體管B極等於0V因此停震不發射無線電,  輸出位於4V以上, 震盪器的晶體管B極等於4V因此震盪發射無線電, 頻率等於 SAW 的頻率 (EPCOS R801, 說是 315MHZ).

無線電的RF部份, 參考過去學到的, 還是那種電容三點式震盪器, 不過這次她使用的是 SAW (Surface Acoustic Wave) resonator, 中文大約是 [梳子震盪器] [表面聲波共振器] wiki 有說明, 出品 XTAL 的公司大概都有類似的產品, 因為它的樣子就是梳子一樣 (用顯微鏡看得見). 另外她有使用 PCB 刻制的天線, 真的就是 [方波] 的外型. 玩弄這次以後, 對無線電有多了一些理解.

網上有一家設計這玩意的公司網站, 設計資料寫得很豐富, 比對手上這個車鑰匙的設計, 看起來那些資料很靠譜, 值得學習參考, 說不定看完看懂, 除了沒有實作以外, 基本上可以說已經學會了這種遙控器的設計了, 那接收器呢 ?? 有興趣看看以下, 大概會掌握更多,

試圖DIY 簡單FM收音機
https://goo.gl/Lwmm0D

AN13: Colpitts oscillator compared to Pierce oscillator
http://en.tdk.eu/blob/530906/download/3/pdf-an13.pdf

Application Note, SAW-Components, TDK
http://en.tdk.eu/blob/530946/download/3/pdf-an25.pdf

http://blog.solidremote.com/post/rf-remote-control-ook-vs-fsk-modulation.aspx

http://en.tdk.eu/tdk-en/529548/products/product-catalog/rf—saw-components-and-modules/automotive-electronics-remote-control/application-notes/527244

http://www.solidremote.com/imgcdn/solidremote-ook-fsk-modulation.pdf
2016-03-27, 有人問, 上面的那條連接失效了, 看來原作者不再公開放在網路上, 有需要的可以用WEB ACHIVE 看看以前的,
http://web.archive.org/web/20150622165355/http://www.solidremote.com/imgcdn/solidremote-ook-fsk-modulation.pdf

 

http://blog.solidremote.com/post/rf-remote-control-transmitter-development-project-pcb-board-design.aspx

http://blog.solidremote.com/post/rf-remote-control-ook-vs-fsk-modulation.aspx

http://blog.solidremote.com/post/design-of-rf-remote-control-transmitter-using-saw-resonator.aspx

http://blog.solidremote.com/post/saw-resonator-enabled-rf-remote-control-transmitter-design-guide.aspx

http://blog.solidremote.com/post/design-of-rf-remote-control-transmitter-using-saw-resonator.aspx